CN111341842A - Robust heterojunction bipolar transistor structure - Google Patents

Robust heterojunction bipolar transistor structure Download PDF

Info

Publication number
CN111341842A
CN111341842A CN201911293346.4A CN201911293346A CN111341842A CN 111341842 A CN111341842 A CN 111341842A CN 201911293346 A CN201911293346 A CN 201911293346A CN 111341842 A CN111341842 A CN 111341842A
Authority
CN
China
Prior art keywords
layer
emitter
cap layer
emitter cap
semiconductor material
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
CN201911293346.4A
Other languages
Chinese (zh)
Other versions
CN111341842B (en
Inventor
黄朝兴
金宇中
曾敏男
陈凯榆
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Visual Photonics Epitaxy Co Ltd
Original Assignee
Visual Photonics Epitaxy Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Visual Photonics Epitaxy Co Ltd filed Critical Visual Photonics Epitaxy Co Ltd
Publication of CN111341842A publication Critical patent/CN111341842A/en
Application granted granted Critical
Publication of CN111341842B publication Critical patent/CN111341842B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
    • H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
    • H01L29/68—Types of semiconductor device ; Multistep manufacturing processes therefor controllable by only the electric current supplied, or only the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched
    • H01L29/70—Bipolar devices
    • H01L29/72—Transistor-type devices, i.e. able to continuously respond to applied control signals
    • H01L29/73—Bipolar junction transistors
    • H01L29/737—Hetero-junction transistors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
    • H01L29/02—Semiconductor bodies ; Multistep manufacturing processes therefor
    • H01L29/12—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by the materials of which they are formed
    • H01L29/20—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by the materials of which they are formed including, apart from doping materials or other impurities, only AIIIBV compounds
    • H01L29/201—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by the materials of which they are formed including, apart from doping materials or other impurities, only AIIIBV compounds including two or more compounds, e.g. alloys
    • H01L29/205—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by the materials of which they are formed including, apart from doping materials or other impurities, only AIIIBV compounds including two or more compounds, e.g. alloys in different semiconductor regions, e.g. heterojunctions

Landscapes

  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Ceramic Engineering (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • Bipolar Transistors (AREA)

Abstract

A heterojunction bipolar transistor structure with robustness is provided, which comprises a substrate and a multilayer structure formed on the substrate, wherein a first emitter cover layer and a second emitter cover layer or only the emitter cover layer is formed between an emitter layer and an ohmic contact layer in the multilayer structure; in the case of providing the first emitter cap layer and the second emitter cap layer, the first emitter cap layer and the second emitter cap layer are formed on the emitter layer, and the robustness of the HBT is improved by changing the energy gap of the first emitter cap layer or the second emitter cap layer; when an emitter cap layer is provided, the emitter cap layer is arranged between the emitter layer and the ohmic contact layer, and the firmness of the HBT is improved by enabling the electron affinity of at least one part of the emitter cap layer to be smaller than or equal to the electron affinity of the emitter layer.

Description

Robust heterojunction bipolar transistor structure
Technical Field
A transistor structure, especially a heterojunction bipolar transistor structure.
Background
Heterojunction Bipolar Transistors (HBTs) are formed by using different semiconductor materials for the Emitter layer and the base layer, and forming a Heterojunction at the junction of the Emitter layer and the base layer, which is advantageous in that the hole flow from the base layer to the Emitter layer is difficult to cross the Valence Band barrier (△ Ev) between the base layer and the Emitter layer, and particularly when the Emitter material is InGaP, InGaAsP or InAlGaP, the Valence Band barrier of the Emitter layer and the base layer is particularly large, so that the Emitter Injection Efficiency (Emitter Injection Efficiency) is increased, thereby allowing the base to still increase the current gain at a higher doping concentration, and thus improving the high frequency response characteristics of the HBT.
Fig. 1 is a schematic diagram of a HBT structure in the prior art, which shows that the HBT structure 1 sequentially stacks the sub-collector layer 20, the collector layer 30, the base layer 40, the emitter layer 50, the emitter cap layer 60, and the ohmic contact layer 70 from bottom to top on the substrate 10. generally, the emitter layer 50 is formed of InGaP and the emitter cap layer 60 is formed of GaAs, there is a large conduction band discontinuity (△ Ec) at the junction between them, thereby forming a large electron potential barrier, so that, as shown in fig. 3, when electrons pass from the emitter cap layer 60 to the emitter layer 50, the potential barrier of the conduction band impedes the flow of electrons, thereby causing a large emitter resistance (Re) to be generated.
Disclosure of Invention
The present invention has been made to overcome the above-mentioned problems, and it provides a robust heterojunction bipolar transistor structure, which can effectively increase the breakdown voltage of the emitter-base junction and reduce the emitter-base junction capacitance without increasing or slightly increasing the emitter resistance, and can utilize the characteristics of aluminum (Al) containing semiconductor material such as aluminum gallium arsenide (AlGaAs) having higher energy gap and resistivity rapidly increasing with temperature at high temperature to increase the robustness of PA during high power density operation, improve RF characteristics, and further improve the efficiency and Linearity of PA by changing the HBT design manner, such as reducing Re, to sacrifice partially increased PA robustness, thereby improving the overall performance and design flexibility of PA.
In an embodiment of an HBT comprising a first emitter cap layer and a second emitter cap layer, a robust heterojunction bipolar transistor structure comprises: a substrate; a sub-collector layer on the substrate, the sub-collector layer comprising an N-type group III-V semiconductor material; a collector layer on the subcollector layer, the collector layer comprising a group III-V semiconductor material; a base layer on the collector layer, the base layer comprising a P-type group III-V semiconductor material; an emitter layer on the base layer, the emitter layer comprising at least one N-type semiconductor material of InGaP, InGaAsP and InAlGaP; a first emitter cap layer on the emitter layer, the first emitter cap layer comprising III-V semiconductor material; a second emitter cap layer on the first emitter cap layer, the second emitter cap layer comprising III-V semiconductor material; and an ohmic contact layer on the second emitter cap layer, the ohmic contact layer comprising N-type III-V group semiconductor material, wherein, in the direction from the second emitter cap layer to the emitter layer, the energy gap variation of the first emitter cap layer or the second emitter cap layer comprises at least one of the gradual energy gap change from small to large and the energy gap is kept flat.
In one embodiment, the first emitter cap layer comprises at least one semiconductor material selected from the group consisting of: al (Al)xGa1-xAs、AlxGa1-xAs1-yNy、AlxGa1-xAs1-zPz、AlxGa1-xAs1-wSbw、InrAlxGa1-x-rAs and InrAlxGa1-x-rP, wherein x is more than 0 and less than 1; or the maximum value of the x value is more than or equal to 0.03 and less than or equal to 0.8; or the maximum value of the x is more than or equal to 0.05 and less than or equal to 0.4, and y, z, r and w are less than or equal to 0.1.
In one embodiment, the first emitter cap layer or the second emitter cap layer comprises at least one uniform layer.
In one embodiment, the first emitter cap layer or the second emitter cap layer comprises at least one graded layer, and the energy gap variation of the graded layer at least comprises gradual change from small to large in the direction from the second emitter cap layer to the emitter layer.
In one embodiment, the first emitter cap layer or the second emitter cap layer comprises a combination of at least one uniform layer and at least one graded layer, and the energy gap variation of the graded layer at least comprises gradual change from small to large in the direction from the second emitter cap layer to the emitter layer.
In one embodiment, the first emitter cap layer or the second emitter cap layer is thickThe degree is 1 nm-500 nm, and the concentration of N-type doping of the first emitter cap layer or the second emitter cap layer is 1 × 1015/cm3～5×1018/cm3。
In one embodiment, the emitter layer is formed of a material having an InGaP emission wavelength of 694nm or less, an InGaAsP emission wavelength of 710nm or less, and an InAlGaP emission wavelength of 685nm or less by Photoluminescence fluorescence spectroscopy (PL).
In one embodiment, the emitter layer is formed of a material having an InGaP emission wavelength of 685nm or less, an InGaAsP emission wavelength of 695nm or less, and an InAlGaP emission wavelength of 675nm or less by photoluminescence spectroscopy.
In one embodiment, the emitter layer is formed by photoluminescence spectroscopy, wherein the emission wavelength of InGaP is 675nm or less, the emission wavelength of InGaAsP is 685nm or less, and the emission wavelength of InAlGaP is 665nm or less.
In one embodiment, the device further comprises an intermediate composite layer between the substrate and the sub-collector layer.
In one embodiment, the intermediate composite layer comprises at least one buffer layer, and the buffer layer comprises a group III-V semiconductor material.
In one embodiment, the intermediate composite layer comprises a field effect transistor.
In one embodiment, the intermediate composite layer comprises a dummy hemt formed on the substrate: the buffer layer, the first doping layer, the first spacing layer, the channel layer, the second spacing layer, the second doping layer, the Schottky layer, the etching stop layer and the top cover layer are used for ohmic contact. The buffer layer comprises a group III-V semiconductor material; the first doped layer or the second doped layer comprises at least one N-type semiconductor material selected from the group consisting of: GaAs, AlGaAs, InAlGaP, InGaP, and InGaAsP; the first spacer layer or the second spacer layer comprises at least one semiconductor material selected from the group consisting of: GaAs, AlGaAs, InAlGaP, InGaP, and InGaAsP; the channel layer comprises at least one material selected from the group consisting of: GaAs, InGaAs, AlGaAs, InAlGaP, InGaP, and InGaAsP; the schottky layer comprises at least one material selected from the group consisting of: GaAs, AlGaAs, InAlGaP, InGaP, and InGaAsP; the etch stop layer comprises at least one material selected from the group consisting of: GaAs, AlGaAs, InAlGaP, InGaAsP, InGaP, and AlAs; the cap layer comprises an N-type group III-V semiconductor material.
In one embodiment, further comprising a spacer layer, said spacer layer being located between said first emitter cap layer and said emitter layer, or said spacer layer being located between said first emitter cap layer and said second emitter cap layer; the spacer layer comprises an N-type doped or undoped III-V semiconductor material.
In one embodiment, the thickness of the spacer layer is 0.2 nm-200 nm, and the N-type doping concentration of the spacer layer is 1 × 1015/cm3～5×1018/cm3。
In one embodiment, the spacer layer comprises at least one material selected from the group consisting of: AlGaAs, AlGaAsN, AlGaAsP, AlGaAsSb, InAlGaAs, InGaP, InGaAsP, InGaAs, InGaAsSb, InAlGaP, and GaAs.
In one embodiment, the energy gap variation of the spacer layer includes at least one of a gradual change from small to large in energy gap, a flat energy gap and a gradual change from large to small in energy gap.
The following examples relate to electron affinity of the emitter cap layer.
A robust heterojunction bipolar transistor structure comprising: a substrate; a sub-collector layer on the substrate, the sub-collector layer comprising an N-type group III-V semiconductor material; a collector layer on the subcollector layer, the collector layer comprising a group III-V semiconductor material; a base layer on the collector layer, the base layer comprising a P-type group III-V semiconductor material; an emitter layer on the base layer, the emitter layer comprising an N-type group III-V semiconductor material; an emitter cap layer on the emitter layer, the emitter cap layer comprising III-V semiconductor material; and an ohmic contact layer on the emitter cap layer, the ohmic contact layer comprising an N-type group III-V semiconductor material; at least one part of the emitter cover layer is a current clamping layer, and the electron affinity of the current clamping layer is smaller than or equal to that of the emitter layer.
Wherein the emitter layer comprises at least one N-type semiconductor material selected from the group consisting of: InGaP, InGaAsP, AlGaAs, and InAlGaP. The current clamping layer comprises at least one material selected from the group consisting of: AlGaAs, AlGaAsN, AlGaAsP, AlGaAsSb, InAlGaAs, InGaP, InGaAsP, GaAsSb, InAlGaP, and GaAs.
In one embodiment, the emitter cap layer comprises at least one uniform layer.
In one embodiment, the emitter cap layer comprises at least one graded layer, and the energy gap of the graded layer at least comprises gradual change from small to large in the direction from the ohmic contact layer to the emitter layer.
In one embodiment, the emitter cap layer comprises a combination of at least one uniform layer and at least one graded layer, and the energy gap variation of the graded layer at least comprises gradual change from small to large in the direction from the ohmic contact layer to the emitter layer.
In one embodiment, the emitter cap layer has a thickness of 1 nm-500 nm, and the N-type doping concentration of the emitter cap layer is 1 × 1015/cm3～5×1018/cm3。
In one embodiment, the emitter layer is formed of a material having an InGaP emission wavelength of 694nm or less, an InGaAsP emission wavelength of 710nm or less, and an InAlGaP emission wavelength of 685nm or less by Photoluminescence fluorescence spectroscopy (PL).
In one embodiment, the emitter layer is formed of a material having an InGaP emission wavelength of 685nm or less, an InGaAsP emission wavelength of 695nm or less, and an InAlGaP emission wavelength of 675nm or less by photoluminescence spectroscopy.
In one embodiment, the emitter layer is formed by photoluminescence spectroscopy, wherein the emission wavelength of InGaP is 675nm or less, the emission wavelength of InGaAsP is 685nm or less, and the emission wavelength of InAlGaP is 665nm or less.
In one embodiment, the device further comprises an intermediate composite layer between the substrate and the sub-collector layer.
In one embodiment, the intermediate composite layer comprises at least one buffer layer, and the buffer layer comprises a group III-V semiconductor material.
In one embodiment, the intermediate composite layer comprises a field effect transistor.
In one embodiment, the intermediate composite layer comprises a dummy hemt formed on the substrate: the buffer layer, the first doping layer, the first spacing layer, the channel layer, the second spacing layer, the second doping layer, the Schottky layer, the etching stop layer and the top cover layer are used for ohmic contact. The buffer layer comprises a group III-V semiconductor material; the first doped layer or the second doped layer comprises at least one N-type semiconductor material selected from the group consisting of: GaAs, AlGaAs, InAlGaP, InGaP, and InGaAsP; the first spacer layer or the second spacer layer comprises at least one semiconductor material selected from the group consisting of: GaAs, AlGaAs, InAlGaP, InGaP, and InGaAsP; the channel layer comprises at least one material selected from the group consisting of: GaAs, InGaAs, AlGaAs, InAlGaP, InGaP, and InGaAsP; the schottky layer comprises at least one material selected from the group consisting of: GaAs, AlGaAs, InAlGaP, InGaP, and InGaAsP; the etch stop layer comprises at least one material selected from the group consisting of: GaAs, AlGaAs, InAlGaP, InGaAsP, InGaP, and AlAs; the cap layer comprises an N-type group III-V semiconductor material.
In one embodiment, further comprising a spacer layer between the emitter cap layer and the emitter layer, or between the emitter cap layer and the ohmic contact layer; the spacer layer comprises an N-type doped or undoped III-V semiconductor material.
In one embodiment, the thickness of the spacer layer is 0.2 nm-200 nm, and the N-type doping concentration of the spacer layer is 1 × 1015/cm3～5×1018/cm3。
In one embodiment, the spacer layer comprises at least one material selected from the group consisting of: AlGaAs, AlGaAsN, AlGaAsP, AlGaAsSb, InAlGaAs, InGaP, InGaAsP, InGaAs, InGaAsSb, InAlGaP, and GaAs.
In one embodiment, the energy gap variation of the spacer layer includes at least one of a gradual change from small to large in energy gap, a flat energy gap and a gradual change from large to small in energy gap.
Drawings
Figure 1 is a schematic diagram of a prior art HBT structure.
Fig. 2 is a schematic diagram of the energy band between the emitter cap layer and the emitter layer in the HBT structure of the prior art.
Figure 3 is a schematic diagram of a HBT structure with robustness according to a first embodiment described, the HBT of the first embodiment comprising a first emitter cap layer and a second emitter cap layer.
Fig. 4a to 4c are schematic energy band diagrams between an emitter cap layer and an emitter layer in an HBT structure according to an embodiment.
Fig. 5 a-5 b are schematic energy band diagrams between an emitter cap layer and an emitter layer in an HBT structure according to an embodiment.
Fig. 6a to 6c are schematic energy band diagrams between an emitter cap layer and an emitter layer in an HBT structure according to an embodiment.
Fig. 7 is a graph of Photoluminescence (PL) spectra of indium gallium phosphide (InGaP) as an emitter layer material according to an embodiment.
FIG. 8 is a graph of emitter-base junction carrier concentration obtained by C-V measurements using different degrees of atomically ordered InGaP as the emitter layer.
Figure 9 is a graph showing a Safe Operating Area (SOA) comparison of the HBT according to figure 6c and a prior art HBT. The vertical axis represents collector current density Jc (kA/cm)2) The horizontal axis represents collector-emitter voltage vce (volt).
Figure 10 is a schematic diagram of a robust HBT structure according to a second embodiment as described, wherein a portion of the emitter cap layer of the second embodiment is a current clamping layer having an electron affinity less than or equal to that of the emitter layer.
Fig. 11a is a schematic diagram showing the relationship between the conduction band of the current clamping layer and the conduction band of the emitter layer.
Fig. 11b is a schematic diagram showing the relationship between the conduction band of the current clamping layer and the conduction band of the emitter layer.
Fig. 11c is a schematic diagram showing the relationship between the conduction band of the current clamping layer and the conduction band of the emitter layer.
Fig. 11d is a schematic diagram showing the relationship between the conduction band of the current clamping layer and the conduction band of the emitter layer.
Description of the symbols
1 HBT structure
2. 3 HBT structure
10 base plate
20. Collector layer 200 times
30. 300 collector layer
40. 400 base layer
50. 500 emitter layer
60. 600 emitter cap layer
62 first emitter cap layer
64 second emitter cap layer
70. 700 ohm contact layer.
Detailed Description
The embodiments of the present invention will be described in detail below with reference to the drawings and the accompanying reference numerals, so that those skilled in the art can implement the embodiments after studying the specification.
Examples of specific elements and arrangements thereof are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to limit the scope of the invention in any way. For example, when reference is made in the description to the first epitaxially grown layer being on top of the second epitaxially grown layer, this may include embodiments in which the first epitaxially grown layer is in direct contact with the second epitaxially grown layer, and may also include embodiments in which other elements or epitaxially grown layers are formed therebetween without direct contact. Moreover, the use of repetitive reference numbers and/or symbols in various embodiments is intended merely to clearly and concisely describe some embodiments and is not intended to represent a particular relationship between the various embodiments and/or structures discussed.
Furthermore, spatially relative terms, such as "below," "lower," "above," "higher," and the like, may be used herein to facilitate describing one element(s) or feature(s) relationship to another element(s) or feature(s) in the drawings. These spatial relationships include the various orientations of the device in use or operation and the orientation depicted in the figures.
The present specification provides different examples to illustrate the technical features of different implementations. For example, reference throughout this specification to "some embodiments" means that a particular feature, structure, or characteristic described in connection with the embodiments is included in at least one embodiment. Thus, the appearances of the phrase "in some embodiments" appearing in various places throughout the specification are not necessarily all referring to the same embodiments.
Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. Further, as used herein, the terms "comprising," having, "" wherein, "or any other variation thereof, are intended to cover a corresponding feature in a similar manner as the term" comprising.
Further, "layer" may be a single layer or include multiple layers; and a "portion" of an epitaxially grown layer may be one layer of the epitaxially grown layer or a plurality of layers adjacent to each other.
Referring to fig. 3, fig. 3 is a schematic diagram of a HBT structure with robustness according to the first embodiment described, as shown in fig. 3, the HBT structure 2 includes a substrate 10, a sub-collector layer 20, a collector layer 30, a base layer 40, an emitter layer 50, a first emitter cap layer 62, a second emitter cap layer 64, and an ohmic contact layer 70.
In the HBT structure 2, the sub-collector layer 20 is on the substrate 10, the sub-collector layer 20 mainly comprising N-type group III-V semiconductor material; collector layer 30 is on subcollector layer 20, collector layer 30 comprising primarily a group III-V semiconductor material; the base layer 40 is on the collector layer 30, the base layer 40 mainly comprising a P-type group III-V semiconductor material; the emitter layer 50 is on the base layer 40, and the emitter layer 50 mainly comprises at least one N-type semiconductor material of InGaP, InGaAsP and InAlGaP; a first emitter cap layer 62 on the emitter layer 50, the first emitter cap layer 62 comprising predominantly N-type group III-V semiconductor material; a second emitter cap layer 64 on the first emitter cap layer 62, the second emitter cap layer 64 consisting essentially of N-type III-V semiconductor material; an ohmic contact layer 70 is on the second emitter cap layer 64, the ohmic contact layer 70 comprising primarily N-type group III-V semiconductor material.
The first emitter cap layer 62 comprises AlxGa1-xAs、AlxGa1-xAs1-yNy、AlxGa1-xAs1-zPz、AlxGa1-xAs1- wSbw、InrAlxGa1-x-rAs and InrAlxGa1-x-rAt least one undoped or N-doped semiconductor material of P, wherein x has a value 0 < x < 1; or the maximum value of the x value is more than or equal to 0.03 and less than or equal to 0.8; or the maximum value of the x is more than or equal to 0.05 and less than or equal to 0.4, and y, z, r and w are less than or equal to 0.1.
The materials of the sub-collector layer 20, the collector layer 30, the base layer 40, the second emitter cap layer 64 and the ohmic contact layer 70 are not limited as long as they are semiconductor materials capable of operating the HBT structure 2, but may be selected as appropriate according to the needs; the sub collector layer 20 includes at least one of N-type GaAs, AlGaAs, InGaP, and InGaAsP; the collector layer 30 comprises at least one of GaAs, AlGaAs, InGaP, and InGaAsP, the semiconductor materials are P-doped, N-doped, or undoped, but preferably at least a portion of the semiconductor materials are N-doped; the base layer 40 comprises at least one of P-type GaAs, GaAsSb, InGaAs, and InGaAsN; the second emitter cap layer 64 includes at least one of N-type GaAs, AlGaAs, InGaP, InGaAsP, AlGaAsN, AlGaAsP, AlGaAsSb, inalgas, InAlGaP, and InGaAs; and the ohmic contact layer 70 comprises at least one of N-type GaAs and InGaAs.
Wherein, the first emitter cap layer 62 or the second emitter cap layer 64 changes through the composition of the semiconductor material, so that the energy gap change of the first emitter cap layer 62 or the second emitter cap layer 64 can include at least one of the gradual change of the energy gap from small to large and the leveling of the energy gap in the direction from the second emitter cap layer 64 to the emitter layer 50 (i.e. in the direction from the ohmic contact layer to the emitter layer); the graded bandgap of the first emitter cap layer 62 can start with the bandgap of the second emitter cap layer 64, but is not limited thereto; or the energy gap of the second emitter cap layer 64 may be graded from the energy gap of the ohmic contact layer, but is not limited thereto. This reduces or eliminates the conduction band barrier encountered by electrons passing from the ohmic contact layer 70 to the emitter layer 50 when the emitter-base junction of the HBT is forward biased, thereby improving the high frequency response and robustness of the HBT.
The energy gap variation of the first emitter cap layer 62 or the second emitter cap layer 64 at least comprises a uniform layer, a graded layer or a uniform layer and a graded layer.
Specifically, in one embodiment, first emitter cap layer 62 comprises at least one graded layer formed of at least one undoped or N-type semiconductor material, but not limited to, AlGaAs, AlGaAsN, AlGaAsP, AlGaAsSb, InAlGaP, and inalgas, with a graded Al composition, and the Al composition is graded from less to more in the direction of second emitter cap layer 64 toward emitter layer 50. Since the larger the Al component, the larger the energy gap of the first emitter cap layer 62, the energy gap of the first emitter cap layer 62 gradually increases from small to large in the direction from the second emitter cap layer 64 toward the emitter layer 50. Thus, when the first emitter cap layer 62 comprises a graded layer and the energy gap of the graded layer gradually changes to a linear gradient, as shown in fig. 4a, the energy gap of the first emitter cap layer 62 shows a linear gradient between the second emitter cap layer 64 and the emitter layer 50, so that when the emitter-base junction of the HBT is forward biased, electrons pass between the second emitter cap layer 64 and the emitter layer 50, the conduction band barrier encountered becomes less significant, thus effectively reducing the emitter resistance.
Although fig. 4a shows an embodiment in which the energy gap of the first emitter cap layer is linearly graded, the energy gap grading of the graded layer may be adjusted to be a gradient curve grading (non-linear) through composition grading, so that the energy gap of the first emitter cap layer 62 is non-linearly graded, to effectively reduce the emitter resistance. The result is presented in fig. 4 b.
Alternatively, the first emitter cap layer 62 may be two or more graded layers, and fig. 4c shows an embodiment in which the first emitter cap layer 62 includes one linearly-changing energy gap graded layer and one non-linearly-changing energy gap graded layer, but the invention is not limited thereto, and may also include multiple linearly-changing energy gap graded layers, multiple non-linearly-changing energy gap graded layers, or multiple energy gap graded layers combining linear and non-linear changes, as required.
Although fig. 4a to 4c only show embodiments in which the conduction band of the first emitter cap layer 62 is as high as the conduction band of the emitter layer 50 at the end, the conduction band of the first emitter cap layer 62 may be made lower than the conduction band of the emitter layer 50 (Type I band alignment) or the conduction band of the first emitter cap layer 62 may be made higher than the conduction band of the emitter layer 50 (Type II band alignment) by adjusting the material composition.
Further, the material composition ratio in the first emitter cap layer 62 is explained. With Al0.03Ga0.97As0.9P0.1For example (Al)xGa1-xAs1-zPzX is 0.03 and z is 0.1), which shows that when the total number of moles of group III elements (Al and Ga) is equal to the total number of moles of group V (As and P), the molar ratio between the elements is Al: ga: as: p: 3: 97: 90: 10. with respect to the composition of Al, the phrase "the highest value of x is 0.03. ltoreq. x.ltoreq.0.8" means that the first emitter cap layer 62 may have different Al contents everywhere even at least one of the places may contain no Al because of the gradual composition, but only if the Al content at one of the places is the highest and the highest content falls within 0.03. ltoreq. x.ltoreq.0.8. When the maximum content of Al in the first emitter cap layer 62 is x ≥ 0.03, compared with the existing GaAs emitter cap layer, the electronic potential barrier between the first emitter cap layer 62 and the emitter layer 50 can be reduced or even a second type energy band connection mode is formed, and the potential barrier between the first emitter cap layer 62 and the emitter layer is eliminated; when the maximum content of the Al component is less than or equal to 0.8, the risk of HBT reliability reduction caused by excessive Al component can be avoided or reduced.
In one embodiment, first emitter cap layer 62 comprises at least one substantially uniform layer of material and is formed primarily of at least one undoped or N-type semiconductor material of AlGaAs, AlGaAsN, AlGaAsP, AlGaAsSb, InAlGaP, and inalgas. When the first emitter cap layer 62 is a uniform layer, i.e. under the condition of constant composition, the energy band diagram is as shown in fig. 5a, the energy gap of the first emitter cap layer 62 is in a flat state, and the potential energy of the conduction band can be between the conduction band of the second emitter cap layer 64 and the emitter layer 50 through the matching and selection of appropriate materials. Fig. 5a also shows that the conduction band between the second emitter cap layer 64 and the emitter layer 50 changes stepwise through the first emitter cap layer 62, so that the conduction band barrier to be overcome each time when electrons pass through is relatively small, thereby reducing the emitter resistance between the second emitter cap layer 64 and the emitter layer 50.
In addition, the first emitter cap layer 62 can be a uniform layer with more than two layers, and fig. 5b shows an embodiment where the first emitter cap layer 62 comprises two uniform layers, and by changing the composition (for example, by increasing the Al content), the potential energy level of the conduction band of the uniform layer is increased layer by layer, so that the potential barrier of each conduction band in the conduction band between the second emitter cap layer 64 and the emitter layer 50 is relatively smaller, and thus the emitter resistance between the second emitter cap layer 64 and the emitter layer 50 can be further reduced.
Although fig. 5a and 5b only show the embodiment in which the conduction band of the first emitter cap layer 62 is lower than the conduction band of the emitter layer 50, the conduction band of the first emitter cap layer 62 may be made equal in height to the conduction band of the emitter layer 50 or the conduction band of the first emitter cap layer 62 may be made higher than the conduction band of the emitter layer 50 by adjusting Al or other components.
In one embodiment, the first emitter cap layer 62 comprises a combination of at least one uniform layer and at least one graded layer, the uniform layer is mainly formed by at least one of undoped or N-type semiconductor of AlGaAs, AlGaAsN, AlGaAsP, AlGaAsSb, InAlGaP and InAlGaAs, the graded layer is mainly formed by at least one of undoped or N-type semiconductor material of AlGaAs, AlGaAsN, AlGaAsP, AlGaAsSb, InAlGaP and InAlGaAs with graded composition, and the energy gap of the graded layer is in the direction from the second emitter cap layer 64 to the emitter layer 50The change comprises at least gradual change from small to large, in the case that the first emitter cap layer 62 sequentially comprises a gradual change layer with a gradually changing linear energy gap and a uniform layer in the direction from the second emitter cap layer 64 to the emitter layer 50 as shown in FIG. 6a, the conduction band between the second emitter cap layer 64 and the emitter layer 50 is changed in a linear increasing manner first and then is leveled again, in the case that the first emitter cap layer 62 sequentially comprises a gradual change layer with a gradually changing linear energy gap, a uniform layer and a gradual change layer with a gradually changing linear energy gap as shown in FIG. 6b, the conduction band between the second emitter cap layer 64 and the emitter layer 50 is increased in a linear increasing manner first, then is leveled and then is increased linearly, wherein the slope of the linear increasing of the first and the second uniform layers may be the same or different from the previous and subsequent linear increasing layers, in combination of at least one gradual change layer is not limited thereto, and a plurality of uniform layers, a graded layers of graded emitter cap layers stacked to form an embodiment with a uniform gap and a gap maintaining level and a multi-step HBT 2, or a uniform emitter cap layer composition is obtained by stacking the first emitter cap layer 62, the gradual change layer 62, the first emitter cap layer 62, the gradual change layer comprises a uniform emitter cap layer with a uniform emitter cap layer composition of a gradual change from a gradual change layer gradient Al 0.0, a uniform emitter cap layer composition, a uniform emitter cap layer of a uniform emitter cap layer composition, a gradual change layer composition, a uniform emitter cap layer composition, a uniform18/cm3。
According to the above description, the bandgap grading of the first emitter cap layer 62 or the second emitter cap layer 64 can start from the bandgap of the second emitter cap layer 64 or the ohmic contact layer 70 through the adjustment of the composition in the semiconductor material, but is not limited thereto, and the bandgap grading can be at least one of linear, non-linear, and step-like or a combination thereof. Wherein the energy gap of the first emitter cap layer 62 or the second emitter cap layer 64 comprises at least one or more energy gaps before, during or after the gradual change from small to large.
Regarding the manufacturing conditions of the first emitter cap layer 62, the degree of improvement of the robustness and the like are considered in view of the manufacturing difficultyAnd the influence on the emitter resistance, the thickness of the first emitter cap layer 62 may be 1 nm-500 nm, preferably 10 nm-300 nm, and most preferably 20 nm-200 nm, and the concentration of N-type dopant in the first emitter cap layer 62 is 1 × 10 in consideration of the influence of the dopant concentration on the breakdown voltage and the emitter-base junction capacitance15/cm3～5×1018/cm3Preferably 1 × 1017/cm3～4×1018/cm3Most preferably 3 × 1017/cm3～3×1018/cm3The thickness of the second emitter cap layer 64 can be 1 nm-500 nm, and the N-type doping concentration of the second emitter cap layer 64 is 1 × 1015/cm3～5×1018/cm3。
According to one embodiment, the first emitter cap layer 62 or the second emitter cap layer 64 can reduce or eliminate the conduction band barrier of electrons from the ohmic contact layer 70 to the emitter layer 50 by adjusting the composition of the semiconductor material (e.g., adjusting the Al composition), and particularly, the formation of Type ii band-gap junction can further reduce the emitter resistance (Re). Therefore, the first emitter cap layer 62 does not need to use a high N-type doping concentration, so that the breakdown voltage of the emitter-base junction can be greatly increased without increasing the emitter resistance, and the capacitance of the emitter-base junction can be greatly reduced to improve the high frequency response characteristic or robustness of the HBT. Furthermore, since the bandgap of the emitter cap layer of the selected semiconductor material containing Al component is generally larger than that of the existing GaAs emitter cap layer, the emitter cap layer with larger bandgap can further improve the breakdown voltage of the emitter-base junction and the robustness of HBT. Meanwhile, the first emitter cap layer 62 containing Al is mainly made of a semiconductor material such as AlGaAs, which has a material characteristic that the rate of increase of resistivity with temperature is relatively high at a high temperature compared to GaAs. When the HBT is operated at high power density, the emitter temperature rises, and the first emitter cap layer 62 or the second emitter cap layer 64 using a material mainly containing AlGaAs rises rapidly due to the emitter temperature under high power density operation, so that the emitter resistance rises rapidly to function as protection of the HBT, thereby increasing the robustness of the HBT. While HBT is operated at normal operating power density, the first emitter cap layer 62 or the second emitter cap layer 64, which is mainly made of AlGaAs, does not add extra emitter resistance at normal operating temperature for the above reasons, and thus does not significantly adversely affect the high frequency response characteristics of HBT and PA.
In addition, InGaP, InGaAsP or InAlGaP of the emitter layer 50 has different degrees of atomic Ordering (Ordering Effect), which causes Spontaneous Polarization Effect, and the higher degree of atomic Ordering (High Ordering) forms larger Spontaneous Polarization Effect, which causes the smaller energy gap of the material and stronger electric field, and the formed strong electric field will deplete the carriers of the first emitter cap layer 62 on the emitter layer 50, and thus the emitter resistance will increase to affect the RF characteristics of PA. Therefore, by properly applying the Low-level atomic ordered (Low ordered) InGaP, InGaAsP, and InAlGaP emitter layer 50, the depletion of carriers in the first emitter cap layer 62 can be reduced, thereby avoiding the occurrence of a significant negative effect on PA characteristics due to the rise of Re, or avoiding the high design complexity of the first emitter cap layer 62 due to the depletion of carriers under the influence of the electric field of the emitter layer 50, thereby improving the overall electrical characteristics or robustness of the HBT and PA.
Therefore, in one embodiment, to determine the degree of atomic alignment in the emitter layer 50, evaluation is primarily performed using Photoluminescence (PL) spectroscopy. In the method, firstly, the material of the emitter layer 50 is epitaxially grown to a thickness of several hundred nanometers on a substrate by the same process as that for manufacturing the emitter layer 50, then light with a specific wavelength is emitted to the emitter layer material, the emitter layer material absorbs the light and re-emits the light to the outside, and finally, the degree of ordered arrangement of atoms in the emitter layer material is evaluated by measuring the wavelength of the emitted light. The higher the degree of atomic order in the emitter layer, the smaller the energy gap, so the longer the wavelength emitted by the material through the energy gap transition when measuring PL; in contrast, the lower the degree of atomic ordering, the shorter the wavelength emitted.
Fig. 7 is a PL spectrum of indium gallium phosphide (InGaP) measured by photoluminescence spectroscopy. Among them, InGaP with highly atomic-ordered arrangement has a smaller energy gap, so the emission spectrum wavelength of PL is longer 694nm, while InGaP with less atomic-ordered arrangement has a larger energy gap, so the emission spectrum wavelength of PL is shorter 659 nm. In general, the radiation wavelength of InGaP can be as short as 640nm, the radiation wavelength of InGaAsP can be 645nm and the radiation wavelength of InAlGaP can be 635nm in the case of low atomic order, and the radiation wavelength of the emitter layer 50 made of InGaP can be 694nm or less, preferably 685nm or less, more preferably 675nm or less, in order to avoid the generation of a strong electric field due to high atomic order. Similarly, the InGaAsP constituting the emitter layer 50 may emit light having a wavelength of 710nm or less, preferably 695nm or less, and more preferably 685nm or less. The InAlGaP constituting the emitter layer 50 has an emission wavelength of 685nm or less, preferably 675nm or less, more preferably 665nm or less.
FIG. 8 is a graph of emitter-base junction carrier concentration obtained by C-V measurement using InGaP (InGaP) with different degree of atomic order (Ordering Effect) as the emitter layer, wherein the base layer is P-type GaAs, the thickness is 80nm, and the carrier concentration is 4 × 1019/cm3The emitter layer is InGaP with different atoms orderly arranged and the thickness is 40 nm.
The first emitter cap layer is made of Al with a thickness of 6nm0.15Ga0.85As and 30nm thick AlxGa1-xAs bandgap graded layers (x is graded from 0.15 to 0) are sequentially formed on the InGaP emitter layer, and it can be seen from fig. 8 that the InGaP emitter layer with higher atomic order arrangement forms stronger electric field due to larger spontaneous polarization effect, so As to cause more depletion of the first emitter cap layer carriers. This depletion of carriers results in an increase in emitter resistance, which requires an increase in the N-type doping concentration of the first emitter cap layer to reduce depletion of the first emitter cap layer carriers, which, in turn, causes a drop in the emitter-base junction breakdown voltage and an increase in the emitter-base junction capacitance, which negatively affects the robustness or high frequency response characteristics of the HBT and PA. The emitter-base junction carrier concentration diagram of using InGaP emitter layer with lower atomic order arrangement shows that under the emitter layer and the first emitter cap layer with the same doping concentration, the concentration is higherSmall spontaneous polarization effects, the first emitter cap carriers are less depleted and therefore have less negative impact on Re.
Referring to FIG. 9, FIG. 9 is a graph showing a comparison of the Safe Operating Area (SOA) of the HBT of FIG. 6c with a prior art HBT including an emitter cap layer, wherein the total thickness of the first emitter cap layer and the second emitter cap layer of the HBT of FIG. 6c is approximately equal to the total thickness of the emitter cap layer of the prior art HBT, and wherein in FIG. 9 the emitter cap layer of the prior art HBT is N-GaAs with an N-type dopant concentration of approximately 4.0 × 1018/cm3The first emitter cap layer of HBT of FIG. 6c comprises a layer of AlGaAs with gradually changed composition, and a layer of AlGaAs with uniform composition, wherein the gradually changed composition means that Al composition of the first emitter cap layer increases from 0 to 0.2(x value gradually changes from 0 to 0.2) in the direction from the second emitter cap layer to the emitter layer, and the uniformly changed composition means that Al composition is 0.2, and the doping concentration of the first emitter cap layer of HBT is about 1 × 1018/cm3。
It is clear from the figure that the HBT of figure 6c has an SOA greater than that of the prior art HBTs and that the robustness of the HBT is significantly improved.
In one embodiment, the robust HBT structure 2 can further comprise an intermediate composite layer (not shown) formed between the substrate 10 and the sub-collector layer 20 and formed of a semiconductor material.
In one embodiment, the intermediate composite layer includes at least one buffer layer, and the buffer layer is formed from a III-V semiconductor material.
In one embodiment, the intermediate composite layer comprises a field effect transistor.
In one embodiment, the intermediate composite layer comprises dummy hemts that can be formed sequentially on the substrate 10 (the following structures are not shown): at least one buffer layer, a first doping layer, a first spacing layer, a channel layer, a second spacing layer, a second doping layer, a Schottky layer, an etching stop layer and a top cover layer for ohmic contact; the buffer layer is mainly formed by III-V group semiconductor materials, and the first doping layer or the second doping layer is mainly formed by at least one N-type semiconductor material of GaAs, AlGaAs, InAlGaP, InGaP and InGaAsP; the first spacer layer or the second spacer layer is made of at least one semiconductor material of GaAs, AlGaAs, InAlGaP, InGaP and InGaAsP; the channel layer is made of at least one semiconductor material of GaAs, InGaAs, AlGaAs, InAlGaP, InGaP and InGaAsP; the Schottky layer is made of at least one semiconductor material of GaAs, AlGaAs, InAlGaP, InGaP and InGaAsP; the etching stop layer is made of at least one semiconductor material of GaAs, AlGaAs, InAlGaP, InGaAsP, InGaP and AlAs, and the top cover layer is made of N-type III-V semiconductor material.
In one embodiment, the robust HBT structure 2 further comprises a Spacer (not shown) formed between the first emitter cap layer 62 and the emitter layer 50 or between the first emitter cap layer 62 and the second emitter cap layer 64, the Spacer comprising N-doped or undoped III-V semiconductor material, the Spacer being used for adjusting the energy gap variation, reducing the process difficulty, increasing the process yield, as an etch stop layer, an etch stop layer during the etching process, and as a quantum well layer, preferably, the Spacer has a thickness of 0.2nm to 200nm, and the N-type doping concentration can be 1 × 1015/cm3～5×1018/cm3Preferably 1 × 1017/cm3～4×1018/cm3Most preferably 3 × 1017/cm3～3×1018/cm3。
The material of the spacer layer is not limited as long as it is a conventional N-type doped or undoped III-V semiconductor material, but it is preferably formed of at least one N-type doped or undoped semiconductor material of AlGaAs, AlGaAsN, AlGaAsP, AlGaAsSb, InAlGaAs, InGaP, InGaAsP, InGaAs, GaAsSb, InAlGaP and GaAs.
Preferably, the energy gap of the spacer layer can be changed by changing the composition of the semiconductor material, so that the spacer layer comprises at least one of the gradual change from small to large and the gradual change from large to small in the direction from the first emitter cap layer 62 to the emitter layer 50. However, the spacer layer is not limited to a graded layer having a composition change, and may be a uniform layer such that the spacer layer exhibits a uniform energy gap. The spacer layer may also be a combination of a graded layer and a uniform layer, such that the energy gap variation of the spacer layer in the direction from the first emitter cap layer 62 to the emitter layer 50 may include at least one of a gradual energy gap change from small to large, a flat energy gap, and a gradual energy gap change from large to small. Similarly, the bandgap grading manner may further include at least one of a linear grading, a non-linear grading and a step-like grading.
For example, in the case where the conduction band of the first emitter cap layer 62 is lower than the conduction band (Type I bandgap) of the emitter layer 50, a spacer layer at least including a gradually increasing energy gap may be used to reduce or eliminate the conduction band barrier between the first emitter cap layer 62 and the emitter layer 50. In addition, when the conduction band of the spacer layer is higher than the conduction band (Type II band alignment) of the emitter layer 50 after the spacer layer with gradually changed energy gap is introduced, electrons passing through the space layer and the emitter layer 50 will not encounter the bit energy barrier of the conduction band, and as a result, the emitter resistance will not be increased.
In the case where the conductive band of the first emitter cap layer 62 is higher than the conductive band (Type II band alignment) of the emitter layer 50, if a spacer layer including at least a gradually decreasing energy gap as an etch stopper or the like is used, it is found that the conductive band of the spacer layer can be joined to the conductive band of the emitter layer 50. In addition, after the spacer layer is added, the conduction band of the spacer layer may be lower than the emitter layer 50 to generate a conduction band barrier between the spacer layer and the emitter layer 50, but since the spacer layer may be used as a quantum well, the electron energy level of the conduction band of the spacer layer may be quantized, and as a result, the energy level of the electron energy of the spacer layer may be increased. When electrons pass between the spacer layer and the emitter layer 50, the conduction band barrier encountered becomes low and the emitter resistance does not increase significantly. In addition, in some cases, the spacer layer is introduced to have a gradually changing energy gap from small to large in response to the process considerations, so that the conduction band of the spacer layer is higher than that of the emitter layer 50, but the result is also no significant increase in the emitter resistance.
Furthermore, the above description is intended to enable those skilled in the art to understand: when the spacer is used in the improved process, no matter what kind of the bandgap is changed (i.e. at least one of the bandgap is gradually changed from small to large, the bandgap is constant, and the bandgap is gradually changed from large to small), the emitter resistance is not substantially increased, and the change of the bandgap of the spacer is not limited to the above example.
As described in the foregoing embodiments, the first emitter cap layer containing Al can effectively increase the breakdown voltage of the emitter-base junction and reduce the capacitance of the emitter-base junction without increasing or slightly increasing the emitter resistance, and can utilize the material characteristics of AlGaAs-containing materials with larger energy gap and resistivity rising rapidly with temperature at high temperature to improve the robustness or RF characteristics of the power amplifier during high power density operation, and can further improve the efficiency and linearity of the PA by changing the HBT design manner, such as reducing Re, to sacrifice the partially increased PA robustness, thereby improving the overall performance and design flexibility of the PA.
In addition, the larger spontaneous polarization effect caused by the highly atomic ordered arrangement of the material of the emitter layer is avoided, and the emitter resistance is prevented from increasing, so that the RF characteristics of the PA are not affected. Therefore, the PL method is used to evaluate the degree of atomic order of the emitter layer material, and then the InGaP, InGaAsP, InAlGaP emitter layer with lower degree of atomic order can be determined and properly applied, so that the depletion of the carriers in the first emitter cap layer can be reduced, thereby avoiding the negative influence on the PA characteristics caused by the rise of Re, or avoiding the high design complexity caused by the depletion of the first emitter cap layer to overcome the influence of the electric field of the emitter layer, and further improving the overall electrical characteristics or robustness of the HBT and PA.
Figure 10 is a schematic diagram of a HBT structure with robustness in accordance with the second embodiment being described. As shown in fig. 10, HBT structure 3 of the second embodiment has sub-collector layer 200, collector layer 300, base layer 400, emitter layer 500, emitter cap layer 600, and ohmic contact layer 700 formed on substrate 100; at least one part of the emitter cover layer is a current clamping layer, and the electron affinity of the current clamping layer is smaller than or equal to that of the emitter layer.
The material of the emitter layer 500 is at least one N-type semiconductor material selected from the group consisting of: InGaP, InGaAsP, AlGaAs, and InAlGaP;
the material of the current clamping layer is at least one material selected from the group consisting of: AlGaAs, AlGaAsN, AlGaAsP, AlGaAsSb, InAlGaAs, InGaP, InGaAsP, GaAsSb, InAlGaP, and GaAs.
Because the electron affinity of the current clamping layer is less than or equal to that of the emitter layer, when the transistor operates at a higher current density, the electron barrier of the current clamping layer becomes higher, and the current of the transistor is limited when rising to a certain degree, so as to avoid the HBT operating under an excessively high current, thereby reducing the risk of damage of the transistor and improving the firmness of the HBT; the electronic barrier of the current clamping layer becomes higher as the current density increases, and the magnitude of the electronic barrier becoming higher is different according to the material, composition, doping concentration or doping manner of the emitter cap layer, the current clamping layer or the emitter layer.
Fig. 11a to 11d are schematic diagrams showing the relationship between the conduction band of some current clamping layers and the conduction band of the emitter layer. 11 a-11 d, forming a current clamping layer in a portion of the emitter cap layer, the current clamping layer being disposed at different locations of the emitter cap layer; as shown in these diagrams, the position of the current clamping layer is not limited as long as the electron affinity of the current clamping layer of the emitter cap layer is less than or equal to that of the emitter layer. As long as the electron affinity of one part of the emitter cap layer is less than or equal to that of the emitter layer, even if the electron affinity of the other part of the emitter cap layer is greater than that of the emitter layer or no matter whether the current clamping layer is connected with the emitter layer or not, the current clamping layer can still exert the current clamping (current clamping) effect as a whole; for the sake of brevity, only a few figures are shown as representative or exemplary, and it is intended that the present invention encompass the emitter cap layer as long as a portion of the emitter cap layer is provided with the current clamping layer.
It is noted that the emitter cap layer of the HBT of fig. 10 is provided with a current clamping layer having an electron affinity less than or equal to that of the emitter layer; referring to fig. 6c, the electron affinity of a portion of the first emitter cap layer in the HBT is smaller than that of the emitter layer, so the first emitter cap layer also has the effect of current clamping; therefore, according to the embodiments herein, the HBT having the current clamping layer may also have the effect of improving the SOA or improving the robustness.
The first emitter cap layer of the first embodiment and the current clamping layer of the second embodiment both help to improve the robustness of the HBT, and both can be varied in specific technical measures according to different requirements.
The substrate, the sub-collector layer, the base layer and the ohmic contact layer in the second embodiment are the same as the substrate, the sub-collector layer, the base layer and the ohmic contact layer in the first embodiment, and therefore, the details are not repeated, and please refer to the foregoing description.
The HBT with the current clamping layer can further select various embodiments using an intermediate recombination layer or spacer layer, or an intermediate recombination layer or spacer layer, according to implementation requirements; the contents of the intermediate composite layer and the spacer layer are disclosed in the above paragraphs, and therefore, the details are not repeated here, and please refer to the above paragraphs. It is noted that the spacer layer in the second embodiment is disposed on the emitter layer or between the emitter layer and the emitter cap layer.
According to the implementation requirements, each embodiment of the HBT with the current clamping layer can be used with one or some embodiments of the emitter layer in the first embodiment; or the embodiments of the HBT with the current clamping layer can be used in conjunction with an embodiment or embodiments of the bandgap grading (first emitter cap layer or second emitter cap layer) of the first embodiment, respectively; as mentioned above, the bandgap grading includes linear grading, nonlinear grading, step-like grading or a combination thereof, and various embodiments of the emitter layer and the bandgap grading (the first emitter cap layer or the second emitter cap layer) are disclosed in the foregoing, and thus are not described again.
It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

Claims (21)

1. A robust heterojunction bipolar transistor structure, comprising:
a substrate;
a primary collector layer on the substrate, comprising an N-type group III-V semiconductor material;
a collector layer on the sub-collector layer, comprising III-V semiconductor material;
a base layer on the collector layer, comprising a P-type group III-V semiconductor material;
an emitter layer on the base layer, which contains at least one N-type semiconductor material of InGaP, InGaAsP and InAlGaP;
a first emitter cap layer on the emitter layer comprising III-V semiconductor material;
a second emitter cap layer comprising III-V semiconductor material on the first emitter cap layer; and
an ohmic contact layer on the second emitter cap layer and comprising N-type III-V semiconductor material;
wherein, in the direction from the second emitter cap layer to the emitter layer, the energy gap variation of the first emitter cap layer or the second emitter cap layer comprises at least one of the gradual change of the energy gap from small to large and the leveling of the energy gap.
2. The robust heterojunction bipolar transistor structure of claim 1 wherein said first emitter cap layer comprises at least one semiconductor material selected from the group consisting of: al (Al)xGa1-xAs、AlxGa1-xAs1-yNy、AlxGa1-xAs1-zPz、AlxGa1-xAs1-wSbw、InrAlxGa1-x-rAs and InrAlxGa1-x-rP, wherein x is more than 0 and less than 1.
3. The robust heterojunction bipolar transistor structure of claim 1 wherein said first emitter cap layer comprisesAt least one semiconductor material selected from the group consisting of: al (Al)xGa1-xAs、AlxGa1-xAs1-yNy、AlxGa1-xAs1-zPz、AlxGa1-xAs1-wSbw、InrAlxGa1-x-rAs and InrAlxGa1-x-rP, wherein the maximum value of x is more than or equal to 0.03 and less than or equal to 0.8.
4. The robust heterojunction bipolar transistor structure of claim 1 wherein said first emitter cap layer comprises at least one semiconductor material selected from the group consisting of: al (Al)xGa1-xAs、AlxGa1-xAs1-yNy、AlxGa1-xAs1-zPz、AlxGa1-xAs1-wSbw、InrAlxGa1-x-rAs and InrAlxGa1-x-rP, wherein the maximum value of x is more than or equal to 0.05 and less than or equal to 0.4, and y, z, r and w are less than or equal to 0.1.
5. A robust heterojunction bipolar transistor structure according to claim 1,
the first emitter cap layer or the second emitter cap layer at least comprises a uniform layer, a gradient layer or a uniform layer and a gradient layer, and the energy gap change of the gradient layer at least comprises gradual change from small to large in the direction from the second emitter cap layer to the emitter layer.
6. The robust heterojunction bipolar transistor structure of claim 1, wherein said first emitter cap layer or said second emitter cap layer has a thickness of 1nm to 500nm, and said first emitter cap layer or said second emitter cap layer has a concentration of N-type doping of 1 × 1015/cm3～5×1018/cm3。
7. A robust heterojunction bipolar transistor structure as in claim 1 wherein said emitter layer comprises a material having an InGaP emission wavelength of 694nm or less, an InGaAsP emission wavelength of 710nm or less, and an InAlGaP emission wavelength of 685nm or less by photoluminescence spectroscopy.
8. A robust heterojunction bipolar transistor structure as in claim 1 wherein said emitter layer material has an InGaP emission wavelength of 685nm or less, an InGaAsP emission wavelength of 695nm or less, and an InAlGaP emission wavelength of 675nm or less by photoluminescence spectroscopy.
9. A robust heterojunction bipolar transistor structure according to claim 1, wherein the emitter layer material has an InGaP emission wavelength of 675nm or less, an InGaAsP emission wavelength of 685nm or less, and an InAlGaP emission wavelength of 665nm or less by photoluminescence spectroscopy.
10. The robust heterojunction bipolar transistor structure of claim 1 further comprising an intermediate composite layer between said substrate and said subcollector layer.
11. The robust hbt structure of claim 10, wherein said intermediate composite layer comprises at least one buffer layer or a field effect transistor, said buffer layer comprising III-V semiconductor material.
12. A robust heterojunction bipolar transistor structure according to claim 10,
the intermediate composite layer comprises a dummy hemt formed on the substrate: at least one buffer layer, a first doping layer, a first spacing layer, a channel layer, a second spacing layer, a second doping layer, a Schottky layer, an etching stop layer and a top cover layer for ohmic contact; the buffer layer comprises a group III-V semiconductor material; the first doped layer or the second doped layer comprises at least one N-type semiconductor material selected from the group consisting of: GaAs, AlGaAs, InAlGaP, InGaP, and InGaAsP; the first spacer layer or the second spacer layer comprises at least one material selected from the group consisting of: GaAs, AlGaAs, InAlGaP, InGaP, and InGaAsP; the channel layer comprises at least one material selected from the group consisting of: GaAs, InGaAs, AlGaAs, InAlGaP, InGaP, and InGaAsP; the schottky layer comprises at least one material selected from the group consisting of: GaAs, AlGaAs, InAlGaP, InGaP, and InGaAsP; the etch stop layer comprises at least one material selected from the group consisting of: GaAs, AlGaAs, InAlGaP, InGaAsP, InGaP, and AlAs; the cap layer is comprised of an N-type III-V semiconductor material.
13. The robust heterojunction bipolar transistor structure of claim 1 further comprising a spacer layer between said first emitter cap layer and said emitter layer or between said first emitter cap layer and said second emitter cap layer, said spacer layer comprising N-type doped or undoped III-V semiconductor material.
14. The robust HBT structure of claim 13, wherein said spacer layer has a thickness of 0.2nm to 200nm, and said spacer layer has an N-type doping concentration of 1 × 1015/cm3～5×1018/cm3。
15. The robust heterojunction bipolar transistor structure of claim 13 wherein said spacer layer comprises at least one material selected from the group consisting of: AlGaAs, AlGaAsN, AlGaAsP, AlGaAsSb, InAlGaAs, InGaP, InGaAsP, InAlGaP, InGaAs, GaAsSb, and GaAs.
16. The robust heterojunction bipolar transistor structure of claim 13 wherein said gap variation of said spacer layer comprises at least one of a gradual gap variation, a flat gap variation and a gradual gap variation.
17. A robust heterojunction bipolar transistor structure, comprising:
a substrate;
a primary collector layer on the substrate, comprising an N-type group III-V semiconductor material;
a collector layer on the sub-collector layer, comprising III-V semiconductor material;
a base layer on the collector layer, comprising a P-type group III-V semiconductor material;
an emitter layer on the base layer, comprising N-type III-V semiconductor material;
an emitter cap layer on the emitter layer comprising III-V semiconductor material; and
an ohmic contact layer on the emitter cap layer and comprising N-type III-V semiconductor material;
at least one part of the emitter cover layer is a current clamping layer, and the electron affinity of the current clamping layer is smaller than or equal to that of the emitter layer.
18. The robust heterojunction bipolar transistor structure of claim 17 wherein said emitter layer comprises at least one N-type semiconductor material selected from the group consisting of: InGaP, InGaAsP, AlGaAs, and InAlGaP; the current clamping layer comprises at least one material selected from the group consisting of: AlGaAs, AlGaAsN, AlGaAsP, AlGaAsSb, InAlGaAs, InGaP, InGaAsP, GaAsSb, InAlGaP, and GaAs.
19. The robust heterojunction bipolar transistor structure of claim 18 wherein said emitter layer comprises a material having an InGaP emission wavelength of 694nm or less, an InGaAsP emission wavelength of 710nm or less, and an InAlGaP emission wavelength of 685nm or less by photoluminescence spectroscopy.
20. A robust heterojunction bipolar transistor structure as in claim 18 wherein said emitter layer material has an InGaP emission wavelength of 685nm or less, an InGaAsP emission wavelength of 695nm or less, and an InAlGaP emission wavelength of 675nm or less by photoluminescence spectroscopy.
21. The robust heterojunction bipolar transistor structure of claim 18 wherein the emitter layer material has an InGaP emission wavelength of 675nm or less, an InGaAsP emission wavelength of 685nm or less, and an InAlGaP emission wavelength of 665nm or less by photoluminescence spectroscopy.
CN201911293346.4A 2018-12-18 2019-12-16 Heterojunction bipolar transistor structure with firmness Active CN111341842B (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CN2018115484848 2018-12-18
CN201811548484 2018-12-18

Publications (2)

Publication Number Publication Date
CN111341842A true CN111341842A (en) 2020-06-26
CN111341842B CN111341842B (en) 2023-06-13

Family

ID=71182160

Family Applications (1)

Application Number Title Priority Date Filing Date
CN201911293346.4A Active CN111341842B (en) 2018-12-18 2019-12-16 Heterojunction bipolar transistor structure with firmness

Country Status (1)

Country Link
CN (1) CN111341842B (en)

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5719415A (en) * 1995-03-14 1998-02-17 Sharp Kabushiki Kaisha Hetero-junction bipolar transistor
US20020088993A1 (en) * 1999-03-12 2002-07-11 Twynam John K. Heterojunction bipolar transistor capable of restraining the conductivity modulation of the ballast layer
KR20040012518A (en) * 2002-08-02 2004-02-11 소니 가부시끼 가이샤 Semiconductor device
US20040200523A1 (en) * 2003-04-14 2004-10-14 The Boeing Company Multijunction photovoltaic cell grown on high-miscut-angle substrate
CN1956215A (en) * 2005-07-26 2007-05-02 索尼株式会社 Semiconductor device
JP2007335586A (en) * 2006-06-14 2007-12-27 Sony Corp Semiconductor integrated circuit device and its manufacturing method
US8120147B1 (en) * 2007-12-27 2012-02-21 Vega Wave Systems, Inc. Current-confined heterojunction bipolar transistor

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5719415A (en) * 1995-03-14 1998-02-17 Sharp Kabushiki Kaisha Hetero-junction bipolar transistor
US20020088993A1 (en) * 1999-03-12 2002-07-11 Twynam John K. Heterojunction bipolar transistor capable of restraining the conductivity modulation of the ballast layer
KR20040012518A (en) * 2002-08-02 2004-02-11 소니 가부시끼 가이샤 Semiconductor device
US20040200523A1 (en) * 2003-04-14 2004-10-14 The Boeing Company Multijunction photovoltaic cell grown on high-miscut-angle substrate
CN1956215A (en) * 2005-07-26 2007-05-02 索尼株式会社 Semiconductor device
JP2007335586A (en) * 2006-06-14 2007-12-27 Sony Corp Semiconductor integrated circuit device and its manufacturing method
US8120147B1 (en) * 2007-12-27 2012-02-21 Vega Wave Systems, Inc. Current-confined heterojunction bipolar transistor

Also Published As

Publication number Publication date
CN111341842B (en) 2023-06-13

Similar Documents

Publication Publication Date Title
US20130112945A1 (en) Nanowire-based optoelectronic device for light emission
US9385269B2 (en) Semiconductor epitaxial structure and light-emitting device thereof
US20050133821A1 (en) Semiconductor device
CN109671770B (en) Heterojunction bipolar transistor structure with energy gap gradually-changed hole blocking layer
US9853136B2 (en) Directed epitaxial heterojunction bipolar transistor
US5349201A (en) NPN heterojunction bipolar transistor including antimonide base formed on semi-insulating indium phosphide substrate
US10374071B2 (en) Heterojunction bipolar transistor
McAlister et al. Use of dipole doping to suppress switching in indium phosphide double heterojunction bipolar transistors
US7030462B2 (en) Heterojunction bipolar transistor having specified lattice constants
US6768141B2 (en) Heterojunction bipolar transistor (HBT) having improved emitter-base grading structure
CN111341842B (en) Heterojunction bipolar transistor structure with firmness
JP4799938B2 (en) Heterojunction bipolar transistor
TWI727591B (en) Rugged heterojunction bipolar transistor structure
TWI691085B (en) Rugged heterojunction bipolar transistor structure
US11133405B2 (en) High ruggedness heterojunction bipolar transistor
Liu et al. Temperature-dependent study of a lattice-matched InP/InGaAlAs heterojunction bipolar transistor
Rajan et al. III-nitride tunnel junctions and their applications
US11929427B2 (en) High ruggedness heterojunction bipolar transistor (HBT)
US20210226045A1 (en) Heterojunction bipolar transistor
US10818781B2 (en) Heterojunction bipolar transistor structure with a bandgap graded hole barrier layer
JP5098193B2 (en) Heterojunction bipolar transistor
JP5681031B2 (en) Heterojunction bipolar transistor
JP6096503B2 (en) Heterojunction bipolar transistor
CN115207109A (en) Semiconductor epitaxial wafer
CN115566057A (en) Heterojunction bipolar transistor and manufacturing method thereof

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant