CN115986564A

CN115986564A - Quantum cascade laser chip epitaxial layer structure on InP substrate and manufacturing method

Info

Publication number: CN115986564A
Application number: CN202211438600.7A
Authority: CN
Inventors: 杨超; 黄彦; 张盛楠; 高志强; 张宇露; 刘卫亮; 史青; 彭泳卿
Original assignee: Beijing Research Institute of Telemetry; Aerospace Long March Launch Vehicle Technology Co Ltd
Current assignee: Beijing Research Institute of Telemetry; Aerospace Long March Launch Vehicle Technology Co Ltd
Priority date: 2022-11-17
Filing date: 2022-11-17
Publication date: 2023-04-18

Abstract

The invention provides a quantum cascade laser chip epitaxial layer structure on InP substrate and its preparation method, utilize the surface treatment technology of microwave plasma of electron cyclotron resonance to process the surface of the lower waveguide layer at first, provide a high-quality growth surface; then, a phase change buffer layer is inserted between the upper and lower waveguide layers and the active layer to relieve lattice mismatch between the waveguide layers and the active layer strain superlattice, so that interface stress and defects are greatly reduced, and interface quality is improved; and finally, the thickness, the components, the strain, the doping and the interface of the strained superlattice of the active layer are accurately controlled by controlling the switching of the III-V family source of the molecular beam epitaxy. Finally, the high-quality active layer quantum cascade strain superlattice structure with thousands of layers of repeated cycles, specific thickness, small thickness fluctuation, uniform components, no overall stress, uniform doping, steep interface, low roughness and low defect density and the high-quality laser chip epitaxial layer structure are successfully grown on the InP substrate.

Description

Quantum cascade laser chip epitaxial layer structure on InP substrate and manufacturing method

Technical Field

The invention relates to the technical field of semiconductor devices, in particular to an epitaxial layer structure of a quantum cascade laser chip on an InP substrate and a manufacturing method thereof.

Background

The middle and far infrared semiconductor laser with the wavelength of 3-12 mu m has very wide application prospect in the fields of trace gas detection, atmospheric environment remote sensing detection, free space laser communication, directional infrared countermeasure and the like. Among them, quantum Cascade Laser (QCL) has many advantages such as small size, light weight, tunable wavelength, high photoelectric conversion efficiency, etc. as important middle and far infrared semiconductor laser, and has become an important laser light source in middle and far infrared bands. The excellent characteristics of the QCL can be attributed to two characteristics of quantum and cascade, the quantum, namely a QCL core active layer structure is composed of coupled multiple quantum wells or superlattices, discrete sub-band energy levels are formed in the quantum wells due to quantum size effect, and the positions of the sub-band energy levels can be adjusted by adjusting the thickness, components and other parameters of the quantum wells and potential barriers, so that the lasing wavelength can be adjusted; the cascade structure can continuously generate a plurality of photons, thereby obviously improving the quantum efficiency and the laser output power.

Quantum cascade lasers were first developed successfully by Bell laboratories, USA, 1994, and at the time, they were only able to operate at 10K, emitting weak 4.2 μm infrared laser light. With the continuous improvement of band engineering and epitaxial fabrication technology, the output performance of QCLs is also continuously improved, including the ability to operate at room temperature and high temperature, higher output power, higher electro-optic conversion efficiency, and the like. In order to obtain higher output power and electro-optic conversion efficiency, the characteristics of the active layer material of the laser chip are changed. First, the quantum cascade laser needs to use InP-based In _1-x Ga _x As/In _1-y Al _y A material system of As; secondly, the number of superlattice of active layers of the quantum cascade laser chip usually reaches hundreds or even thousands of layers; finally, and most importantly, in order to inhibit the thermal escape of upper-level carriers and improve the output performance, the superlattice of the InGaAs/InAlAs of the active layer is gradually changed into a stress compensation system which is not matched with the substrate InP lattice from a lattice matching system with the substrate InP, namely In _1-x Ga _x The As layer has compressive strain, and the value of x is more than or equal to 0 and less than 0.47; and In _1-y Al _y The As layer has tensile strain, and the value of y is more than 0.48 and less than or equal to 1. The characteristics of thousands of layers of active layer superlattices and strain per monolayer in high performance quantum cascade laser chips have made it more difficult to obtain high quality thousands of layers, a specific thickness with little thickness fluctuation, uniform composition, overall stress-free, uniform doping, steep interface, low roughness, and low defect density than before. In addition, the epitaxial layer of the laser chip, especially the active layer, is the key core of the quantum cascade laser for lasing, so the epitaxial preparation technology of the chip active layer and the auxiliary waveguide layers thereof belongs to the absolute core technology, and the foreign documents are rarely reported. In conclusion, due to the insufficiency of the epitaxial technology, the quantum cascade strain superlattice of the active layer with high quality is difficult to obtain in China, and the superlattice has thousands of layers with different thicknesses, components, doping and interfaces without fluctuationThe method obtains ideal material parameters, thereby deteriorating the quality of the epitaxial layer of the laser chip and finally seriously influencing the output performance of the laser.

To address the problem of InP-based quantum cascade laser material growth, guo yoga et al in its patent [ publication No.: CN 1741330A ] proposes a structure and a growth method of an InP-based quantum cascade laser material, which calibrates the growth parameters of molecular beam epitaxy by growing a single layer material, and finally grows the material structure of the whole quantum cascade laser epitaxial layer. However, the superlattice of the active layer grown in the patent is lattice-matched InGaAs/InAlAs material, and does not relate to a stress compensation system superlattice material, a phase change buffer layer technology and a molecular beam epitaxy growth control technology. In addition, from the positions of the zero-order diffraction peak and the InP substrate peak, the half width of the diffraction peak, and the number and intensity information of the satellite peaks in the presented X-ray double-crystal diffraction data pattern, it is known that the quality of the grown superlattice is not perfect.

Li aizhen et al in its patent [ publication No.: CN 1731637A ] [ authorization announcement number: CN 100373722C ] [ authorization publication number: CN 100373724C proposes an epitaxial layer, a buffer layer and an uninterrupted growth method of an InP-based quantum cascade laser, the author uses only one gaseous source molecular beam epitaxial device to completely grow the whole InP-based quantum cascade epitaxial layer structure, and the quality control effect on the superlattice InGaAs/InAlAs of an active layer and InP of the buffer layer is better. However, the authors grown superlattice active layers of InGaAs/InAlAs materials that are lattice matched, not involving stress compensation system materials, and buffer layers of InP and not phase change buffer layers. Further, although a switching method of a group V source is mentioned, only a switching process of As and P compounds is described, a state of a group III source shutter at the time of switching of a group V source is not described, and the switching method of a group III source employs a method of normally opening an In source furnace and opening/closing a Ga or Al source shutter, and a method of interrupting a group III source of the present invention are also different. Finally, the positions of a zero-order diffraction peak and an InP substrate peak in a presented X-ray double-crystal diffraction data graph show that the quality of the grown superlattice is not a perfect lattice matching material, lattice mismatch exists in the superlattice, so that residual strain exists in the whole material, and the laser output performance is influenced finally.

Overflow et al in their patent [ grant publication no: CN 104073876B, a molecular beam epitaxy method for improving the interface quality of a heterogeneous material is proposed, and the method obtains high heterogeneous interface quality by researching the switching of a source furnace shutter. However, only the switching process of the group III source is described in the method, the state of the group V source shutter when the group III source is switched is not described, and the switching method of the group V source and the phase change buffer layer technology are not involved. Furthermore, the patent is only concerned with improving the quality of the heterointerface and is not concerned with the performance parameters of superlattice thickness, composition, doping, etc. Finally, the patent contains only one datum of photoluminescence spectra and does not provide a more exact confirmation of high resolution X-ray diffraction (HRXRD) and High Resolution Transmission Electron Microscopy (HRTEM) data of superlattice quality.

Aiming at the quality problem of the strained superlattice of the active layer of the quantum cascade laser, mawst et al in the patent [ publication No.: US 2013/0107903A1]The structure and the growth method of a phase change buffer layer (metallic buffer layer) of a GaAs-based quantum cascade laser are provided, which are used for improving the quality of a superlattice epitaxial material with a lattice constant different from that of a substrate. However, this patent is concerned with InGaAs/InAlAs strained superlattices on GaAs substrates, with InGaP being used as the phase change buffer layer _1-x Sb _x The material is flattened by chemical mechanical polishing CMP, the active layer is grown by MOCVD, and the growth research of the phase change buffer layer based on the InP substrate and the molecular beam epitaxy superlattice material thereof is not involved. Furthermore, this patent does not give any data representative of the superlattice or epitaxial layers of the active layer.

Disclosure of Invention

The invention provides an epitaxial layer structure of a quantum cascade laser chip on an InP substrate and a manufacturing method thereof, aiming at solving the problem of low output power of the quantum cascade laser, and the epitaxial layer structure can obtain an active layer quantum cascade strain superlattice structure with high quality, thousands of layers with repeated periods, specific thickness, small thickness fluctuation, uniform components, no stress on the whole, uniform doping, steep interface, low roughness and low defect density, and a high-quality epitaxial layer structure of the laser chip, thereby being beneficial to improving the output power of the quantum cascade laser.

The invention provides an epitaxial layer structure of a quantum cascade laser chip on an InP substrate, wherein an active layer is of a strain superlattice structure, a phase change buffer layer is arranged between the active layer and the substrate and used for adjusting crystal lattices between the substrate and the active layer, and the phase change buffer layer is a multilayer component gradient alloy layer.

The epitaxial layer structure of the quantum cascade laser chip on the InP substrate comprises a substrate, a lower waveguide layer, a lower phase-change buffer layer, an active layer, an upper phase-change buffer layer, an upper waveguide layer and a contact layer which are sequentially connected from bottom to top as a preferred mode;

the phase change buffer layer comprises a lower phase change buffer layer and an upper phase change buffer layer, the lower phase change buffer layer relieves lattice mismatch between the strain superlattices of the lower waveguide layer and the active layer, and the upper phase change buffer layer relieves lattice mismatch between the strain superlattices of the active layer and the upper waveguide layer;

carrying out surface treatment on the lower waveguide layer by using electron cyclotron resonance microwave plasma, and then growing by using Molecular Beam Epitaxy (MBE) to obtain a lower phase-change buffer layer;

the active layer is a strained superlattice structure.

The invention relates to an epitaxial layer structure of a quantum cascade laser chip on an InP substrate, which is an optimized mode, wherein the substrate is an InP wafer and has the doping concentration of 1 multiplied by 10 ¹⁷ ～1×10 ¹⁸ cm ^-3 Doping n-type Si;

the lower waveguide layer is InP and/or InGaAs material lattice-matched with the substrate, and has a doping concentration of 1 × 10 ¹⁶ ～5×10 ¹⁶ cm ^-3 Doping the n-type Si layer, wherein the thickness of the lower waveguide layer is 1-4 mu m;

the active layer is In _1-x Ga _x As、In _1-y Al _y As repeats 100-500 periods to form a strain superlattice structure, the active layer has a layer thickness of 0.5-6.5 nm, and partial layers of the active layer have a doping concentration of 1 × 10 ¹⁷ ～5×10 ¹⁷ cm ^-3 The n-type Si is doped, x is more than or equal to 0 and less than 0.47, and y is more than 0.48 and less than or equal to 1;

the upper waveguide layer is made of InP and/or InGaAs lattice-matched to the substrate, the upper waveguide layer having a doping concentration of 1 × 10 ¹⁶ ～1×10 ¹⁷ cm ^-3 Doping the n-type Si layer, wherein the thickness of the upper waveguide layer is 1-5 mu m;

the contact layer is InP and/or InGaAs material lattice-matched with the substrate, and the contact layer has doping concentration of 1 × 10 ¹⁸ ～8×10 ¹⁸ cm ^-3 The thickness of the contact layer is 0.1 to 1 μm.

As a preferred mode, the epitaxial layer structure of the quantum cascade laser chip on the InP substrate is characterized in that a lower phase-change buffer layer is transited from a matching system with the substrate to a strain system of an active layer, and an upper phase-change buffer layer is transited from the strain system of the active layer to the matching system of an upper waveguide layer.

As a preferred mode, the epitaxial layer structure of the quantum cascade laser chip on the InP substrate is characterized In that the lower phase change buffer layer is In _1-x Ga _x As and/or In _1-y Al _y A multi-layer component gradient alloy layer formed by one or a combination of As, x is more than or equal to 0 and less than or equal to 0.47, y is more than or equal to 0.48 and less than or equal to 1 _1-x Ga _x The gradient change value Deltax of As component is 0.01-0.05 _1-y Al _y The gradient change value delta y of the As component is 0.01-0.05, the thickness of each layer of the lower phase change buffer layer is 1-10 nm, and the doping concentration of partial layers is 1 multiplied by 10 ¹⁶ ～5×10 ¹⁶ cm ^-3 Doping n-type Si;

the upper phase transition buffer layer is In _1-x Ga _x As and/or In _1-y Al _y A plurality of component gradient alloy layers formed by one or a combination of As, x is more than or equal to 0 and less than or equal to 0.47, y is more than or equal to 0.48 and less than or equal to 1 _1-x Ga _x The gradient change value Deltax of As component is 0.01-0.05 _1-y Al _y The gradient change value delta y of the As component is 0.01-0.05, the thickness of each layer of the lower phase change buffer layer is 1-10 nm, and the doping concentration of partial layers is 1 multiplied by 10 ¹⁶ ～5×10 ¹⁶ cm ^-3 Is doped with n-type Si.

The invention provides a manufacturing method of an epitaxial layer structure of a quantum cascade laser chip on an InP substrate, which comprises the following steps:

s1, cleaning a substrate;

s2, growing a lower waveguide layer;

s3, performing surface treatment on the lower waveguide layer by using an ECR microwave plasma system;

s4, growing a phase-change buffer layer;

s5, growing an active layer and obtaining a quantum cascade strain superlattice;

s6, growing a phase change buffer layer;

s7, growing an upper waveguide layer;

and S8, growing a contact layer to obtain the epitaxial layer structure of the laser chip.

The invention relates to a method for manufacturing an epitaxial layer structure of a quantum cascade laser chip on an InP substrate, which is a preferable mode, step S1 is to clean the substrate by using a chemical method, and the step S1 comprises the following steps:

s11, immersing the substrate in a boiled electronic pure acetone solvent and an absolute ethyl alcohol solvent in sequence, and carrying out ultrasonic cleaning for 1-3 times, 1-5 min each time; then, leaching the substrate with deionized water at least twice, wherein the substrate is an InP wafer;

s12, taking out the substrate in the step S11, placing the substrate in a mixed solution composed of concentrated sulfuric acid, hydrogen peroxide and water according to a volume ratio of 5; then, rinsing the substrate with deionized water at least twice;

s13, taking out the substrate in the step S12, and drying the substrate in a vacuum drying oven at the temperature of 100-150 ℃ for 0.5-1 h to obtain a cleaned substrate;

in the step S2, growing a lower waveguide layer on the cleaned substrate by using Molecular Beam Epitaxy (MBE) or Metal Organic Chemical Vapor Deposition (MOCVD);

the cleaned substrate is dehydrated and degassed in a pretreatment chamber, the pretreatment temperature is 100-200 ℃, and the pretreatment time is 1-2 h; after the pretreatment is finished, the substrate is conveyed to a growth chamber to carry out epitaxial growth of a lower waveguide layer, the growth temperature of MBE is 450-550 ℃, and the growth temperature of MOCVD is 600-760 ℃;

the method further comprises a step S9 of manufacturing a laser on the epitaxial layer structure of the laser chip to obtain the laser;

quantum cascade laser fabrication on epitaxial layer structure of laser chip, including deposition of SiO ₂ Photoetching to determine ridge waveguide, corroding, secondary epitaxial InP, photoetching to determine an electrode window, thinning a substrate, manufacturing an electrode, cleaving, coating a film, flip-chip bonding, gold wire ball bonding and packaging to obtain the laser.

The invention relates to a method for manufacturing an epitaxial layer structure of a quantum cascade laser chip on an InP substrate, and as a preferable mode, the step S3 comprises the following steps:

s31, putting the wafer with the waveguide grown in the step S2 into a sample tray, and pushing the wafer into a discharge chamber of an ECR microwave plasma system through a sample sending rod;

s32, sequentially turning on a mechanical pump and a molecular pump for vacuum treatment, and when the vacuum degree reaches 10 ^-6 Heating and raising the temperature when the pressure is lower than Pa, and carrying out dehydration and degassing pretreatment on the wafer, wherein the pretreatment temperature is 100-200 ℃, and the pretreatment time is 1-2 h;

s33, after the pretreatment is finished, setting the temperature to be required, introducing a plasma excitation gas source, and starting the ECR microwave plasma surface treatment; the plasma excitation gas source is H ₂ Mixed gas of/Ar, H ₂ The volume ratio in the mixed gas is 0.1-5%, the total mixing flow is 20-60 sccm, the microwave power is 300-800W, the treatment temperature is 200-400 ℃, and the treatment time is 1-20 min.

The invention relates to a manufacturing method of an epitaxial layer structure of a quantum cascade laser chip on an InP substrate, which is characterized in that in a preferable mode, in step S4, a phase-change buffer layer is grown on a wafer subjected to surface treatment by Electron Cyclotron Resonance (ECR) microwave plasma in step S3 by using Molecular Beam Epitaxy (MBE);

firstly, conveying a wafer to a pretreatment chamber, and performing degassing and dehydration treatment at the pretreatment temperature of 100-200 ℃ for 1-2 h; after the pretreatment is finished, the wafer is conveyed to a growth chamber to carry out epitaxial growth on a phase-change buffer layer, the growth temperature is 450-550 ℃, the growth rate is 0.1-1 nm/s, the beam flow ratio of the V group/III group elements is 5-25, and the rotation speed of the substrate is 5-15 r/min during growth;

in step S5, on the wafer of the phase-change buffer layer after the growth in step S4, continuously growing an active layer by using Molecular Beam Epitaxy (MBE), wherein the active layer is a quantum cascade strain superlattice, the growth temperature is 450-550 ℃, the growth rate is 0.1-1 nm/S, the beam flow ratio of the V group element to the III group element is 5-25, and the rotation speed of the wafer is 5-15 r/min during growth;

in step S6, continuously growing an upper phase-change buffer layer on the wafer on which the quantum cascade strain superlattice of the active layer is grown in step S5 by using Molecular Beam Epitaxy (MBE), wherein the growth temperature is 450-550 ℃, the growth rate is 0.1-1 nm/S, the beam flow ratio of the V group element to the III group element is 5-25, and the rotation speed of the substrate is 5-15 revolutions per minute during growth;

in the step S7, growing an upper waveguide layer on the wafer of which the phase change buffer layer is grown in the step S6 by using Molecular Beam Epitaxy (MBE) or Metal Organic Chemical Vapor Deposition (MOCVD), wherein the growth temperature of the MBE is 450-550 ℃, and the growth temperature of the MOCVD is 600-760 ℃;

in step S8, on the wafer with the upper waveguide layer grown in step S7, a molecular beam epitaxy MBE or metal organic chemical vapor deposition MOCVD is used for growing a contact layer, wherein the growth temperature of the molecular beam epitaxy MBE is 450-550 ℃, and the growth temperature of the metal organic chemical vapor deposition MOCVD is 600-760 ℃.

The manufacturing method of the epitaxial layer structure of the quantum cascade laser chip on the InP substrate, which is disclosed by the invention, is a preferable mode, the step S5 comprises the switching of a shutter of a III-group source furnace, and the specific switching mode comprises the following steps:

when the InGaAs layer is switched to the InAlAs layer, firstly, closing shutters of an In source furnace and a Ga source furnace In the previous step; secondly, the shutter of the As source furnace is normally opened, the vacuum pump pumps away the residual In and Ga sources In the previous step, and the III-group source is interrupted for 0-5 s; finally, simultaneously opening shutters of an In source furnace and an Al source furnace to grow InAlAs;

s II, when the InAlAs layer is switched to the InGaAs layer, firstly, closing the shutters of the In source furnace and the Al source furnace In the previous step; secondly, the shutter of the As source furnace is normally opened, the vacuum pump pumps away the residual In and Al sources In the previous step, and the III-group source is interrupted for 0-5 s; finally, simultaneously opening shutters of the In source furnace and the Ga source furnace to grow InGaAs;

in the step S7, when MBE is used for growth and the material of the upper waveguide layer is InP, switching is carried out on a shutter of the V-group source furnace;

the switching method comprises the following steps: when switching from the InGaAs layer or the InAlAs layer to the InP layer, firstly, closing the shutter of the In source furnace, the Ga source or the Al source furnace In the previous step; secondly, continuously opening an As source furnace shutter, and pumping residual In and Ga sources In the previous step by a vacuum pump; then, closing the As source furnace shutter and simultaneously rapidly opening the P source furnace shutter, and pumping away the residual As source in the previous step by a vacuum pump; finally, opening an In source furnace shutter to grow InP;

in the step S8, when MBE is used for growth and the material of the contact layer is InGaAs, switching of a shutter is carried out by a V-group source furnace;

the switching method comprises the following steps: when the InP layer is switched to the InGaAs layer, firstly, the shutter of the In source furnace In the previous step is closed; secondly, continuously opening a P source furnace shutter, and pumping away the residual In source In the previous step by a vacuum pump; then, closing a P source furnace shutter and simultaneously quickly opening an As source furnace shutter, and pumping away the residual P source in the previous step by a vacuum pump; and finally, simultaneously opening an In source furnace shutter and a Ga source furnace shutter to grow the InGaAs.

In order to solve the problem of low output power of the quantum cascade laser, the technical scheme adopted by the invention is a quantum cascade laser chip epitaxial layer structure on an InP substrate and a manufacturing method thereof, and the quantum cascade laser chip epitaxial layer structure comprises the following two aspects:

as a first aspect of the present invention, the present invention provides an epitaxial layer structure of a quantum cascade laser chip on an InP substrate, comprising from bottom to top: the optical waveguide device comprises a substrate, a lower waveguide layer, a lower phase-change buffer layer, an active layer, an upper phase-change buffer layer, an upper waveguide layer and a contact layer.

Wherein the substrate is InP material and doped with n-type Si with a doping concentration of 1 × 10 ¹⁷ ～1×10 ¹⁸ cm ^-3 ；

Wherein the lower waveguide layer is InP and/or InGaAs material lattice-matched with the substrate, the layer thickness is 1-4 μm, the lower waveguide layer is doped with n-type Si, and the doping concentration is 1 × 10 ¹⁶ ～5×10 ¹⁶ cm ^-3 ；

Wherein the lower phase-change buffer layer is In _1-x Ga _x As and/or In _1-y Al _y A plurality of composition gradient alloy layers formed by one or a combination material in As, wherein the value of x is related to the strain InGaAs alloy composition of the active layer and ranges from 0 to 0.47, the composition gradient change value delta x in the phase change buffer layer is 0.01 to 0.05, the value of y is related to the strain InAlAs alloy composition of the active layer and ranges from 0.48 to 1, the composition gradient change value delta y in the phase change buffer layer is 0.01 to 0.05, the thickness of each layer is 1 to 10nm, each layer is doped with n-type Si, and the doping concentration is 1 multiplied by 10 ¹⁶ ～5×10 ¹⁶ cm ^-3 ；

Wherein the active layer is In _1-x Ga _x As/In _1-y Al _y The two As materials are in a strain superlattice structure formed by repeating 100-500 periods, the value range of x is more than or equal to 0 and less than 0.47, the value range of y is more than 0.48 and less than or equal to 1, the thickness of each layer is 0.5-6.5 nm, certain layers are doped with n-type Si, and the doping concentration is 1 multiplied by 10 ¹⁷ ～5×10 ¹⁷ cm ^-3 ；

Wherein the upper phase transition buffer layer is In _1-x Ga _x As and/or In _1-y Al _y A plurality of component gradient alloy layers formed by one or a combination of As materials, wherein the material characteristics are similar to those of the lower phase-change buffer layer;

wherein the upper waveguide layer is InP and/or InGaAs material lattice-matched with the substrate, the layer thickness is 1-5 μm, the upper waveguide layer is doped with n-type Si with the doping concentration of 1 × 10 ¹⁶ ～1×10 ¹⁷ cm ^-3 ；

Wherein the contact layer is InP and/or InGaAs material lattice-matched with the substrate, the layer thickness is 0.1-1 μm, the contact layer is doped with n-type Si with the doping concentration of 1 × 10 ¹⁸ ～8×10 ¹⁸ cm ^-3 ；

As a second aspect of the present invention, the present invention provides an epitaxial layer structure of a quantum cascade laser chip on an InP substrate and a method for manufacturing the same, characterized by comprising the steps of:

step 1, chemically cleaning and drying an InP wafer, and specifically comprises the following substeps:

(a) And immersing the InP wafer in boiling electronic pure acetone solvent and absolute ethyl alcohol solvent in sequence, and ultrasonically cleaning for 1-3 times, 1-5 min each time. Then, leaching the InP wafer for several times by using deionized water;

(b) Taking out the InP wafer in the substep (a), placing the InP wafer in a mixed solution of concentrated sulfuric acid, hydrogen peroxide and water according to a volume ratio of 5. Then, leaching the InP wafer for several times by using deionized water;

(c) Taking out the InP wafer in the substep (b), and drying the InP wafer in a vacuum drying oven at 100-150 ℃ for 0.5-1 h;

and 2, growing a lower waveguide layer on the InP wafer chemically cleaned in the previous step by adopting Molecular Beam Epitaxy (MBE) or Metal Organic Chemical Vapor Deposition (MOCVD). Firstly, the wafer needs to be dehydrated and degassed in a pretreatment chamber, the pretreatment temperature is 100-200 ℃, and the pretreatment time is 1-2 h. After the pretreatment is finished, the wafer is conveyed to a growth chamber to carry out epitaxial growth of a lower waveguide layer, wherein the growth temperature of MBE is 450-550 ℃, and the growth temperature of MOCVD is 600-760 ℃;

and 3, putting the wafer on which the lower waveguide is grown in the previous step into a sample tray, and pushing the wafer into a discharge chamber of an ECR microwave plasma system through a sample feeding rod. Then, the mechanical pump and the molecular pump are started to perform vacuum treatment in sequence, and when the vacuum degree reaches 10 ^-6 Heating and raising the temperature when the pressure is lower than Pa, and performing dehydration and degassing pretreatment on the wafer at the pretreatment temperature of 100-200 ℃ for 1-2 h. After the pretreatment is finished, setting the temperature to be required, introducing a plasma excitation gas source, and starting the ECR microwave plasma surface treatment. The exciting gas source of the electron cyclotron resonance microwave plasma is H ₂ Mixed gas of/Ar, H ₂ The volume ratio in the mixed gas is 0.1-5%, the total mixing flow is 20-60 sccm, the microwave power is 300-800W, the treatment temperature is 200-400 ℃, and the treatment time is 1-20 min;

and 4, growing a phase-change buffer layer on the wafer subjected to the ECR microwave plasma surface treatment in the last step by adopting Molecular Beam Epitaxy (MBE). Firstly, the wafer is conveyed to a pretreatment chamber for degassing and dehydration treatment, the pretreatment temperature is 100-200 ℃, and the pretreatment time is 1-2 h. After the pretreatment is finished, the wafer is conveyed to a growth chamber to carry out phase-change buffer layer under epitaxial growth, the growth temperature is 450-550 ℃, the growth rate is 0.1-1 nm/s, the beam flow ratio of the V group/III group elements is 5-25, and the rotation speed of the substrate is 5-15 r/min during growth. The switching of the shutter of the III-family source furnace may be involved in growing the lower phase-change buffer layer, and the specific switching mode refers to the following step 5;

and 5, on the wafer of the phase-change buffer layer after the last step of growth, continuously growing the quantum cascade strain superlattice of the active layer by adopting Molecular Beam Epitaxy (MBE), wherein the growth temperature is 450-550 ℃, the growth rate is 0.1-1 nm/s, the beam flow ratio of the V group element to the III group element is 5-25, the rotation speed of the substrate during growth is 5-15 r/min, and the switching of the shutter of the III group source furnace is involved when the strain superlattice structure of the active layer is grown, and the specific switching mode is as follows:

(a) When switching from the InGaAs layer to the InAlAs layer, firstly, closing the shutters of the In source furnace and the Ga source furnace In the previous step; secondly, the shutter of the As source furnace is normally opened, the vacuum pump pumps away the residual In and Ga sources In the previous step, and the III-group source is interrupted for 0-5 s; finally, simultaneously opening shutters of the In source furnace and the Al source furnace to grow InAlAs;

(b) When the InAlAs layer is switched to the InGaAs layer, firstly, closing the shutters of the In source furnace and the Al source furnace In the previous step; secondly, the shutter of the As source furnace is normally opened, the vacuum pump pumps away the residual In and Al sources In the previous step, and the III-group source is interrupted for 0-5 s; finally, simultaneously opening shutters of the In source furnace and the Ga source furnace to grow InGaAs;

step 6, on the wafer on which the quantum cascade strain superlattice of the active layer is grown in the last step, adopting Molecular Beam Epitaxy (MBE) to continue to grow an upper phase change buffer layer, wherein the growth temperature is 450-550 ℃, the growth rate is 0.1-1 nm/s, the beam flow ratio of the V group element to the III group element is 5-25, the rotation speed of a substrate during growth is 5-15 r/min, the shutter switching of a III group source furnace can be related during the growth of the upper phase change buffer layer, and the specific switching mode refers to step 5;

and 7, growing an upper waveguide layer on the wafer with the upper phase-change buffer layer grown in the previous step by adopting Molecular Beam Epitaxy (MBE) or Metal Organic Chemical Vapor Deposition (MOCVD), wherein the growth temperature of the upper waveguide layer is 450-550 ℃, the growth temperature of the lower waveguide layer is 600-760 ℃, and when the MBE is selected for growth and the upper waveguide layer is selected from InP, switching of a V-group source furnace shutter is involved: when switching from an InGaAs (InAlAs) layer to an InP layer, firstly, closing shutters of an In source furnace and a Ga (Al) source furnace In the previous step; secondly, continuously opening an As source furnace shutter, and pumping residual In and Ga (Al) sources In the previous step away by a vacuum pump; then, closing the shutter of the As source furnace, and simultaneously quickly opening the shutter of the P source furnace, and pumping away the residual As source in the previous step by a vacuum pump; finally, opening an In source furnace shutter to grow InP;

and 8, adopting Molecular Beam Epitaxy (MBE) or Metal Organic Chemical Vapor Deposition (MOCVD) to grow a contact layer on the wafer with the upper waveguide layer grown in the last step, wherein the growth temperature of the Molecular Beam Epitaxy (MBE) is 450-550 ℃, the growth temperature of the Metal Organic Chemical Vapor Deposition (MOCVD) is 600-760 ℃, and when the MBE is selected for growth, the upper waveguide layer is selected from InP, and the contact layer is selected from InGaAs, switching of a shutter of a V-group source furnace is involved: when the InP layer is switched to the InGaAs layer, firstly, the shutter of the In source furnace In the previous step is closed; secondly, continuously opening a P source furnace shutter, and pumping away the residual In source In the previous step by a vacuum pump; then, closing a P source furnace shutter and simultaneously quickly opening an As source furnace shutter, and pumping away the residual P source in the previous step by a vacuum pump; finally, simultaneously opening an In source furnace shutter and a Ga source furnace shutter to grow InGaAs;

step 9, finishing the quantum cascade laser manufacturing on the epitaxial wafer prepared in the previous step, including depositing SiO ₂ The manufacturing method comprises the following process steps of ridge waveguide photoetching determination, corrosion, secondary epitaxial InP, electrode window photoetching determination, substrate thinning, electrode manufacturing, cleavage, film coating, flip chip bonding, gold wire ball bonding and packaging.

The invention has the following advantages:

compared with the prior art, the invention firstly utilizes the surface treatment technology of the electron cyclotron resonance microwave plasma to treat the surface of the lower waveguide layer, the electron cyclotron resonance microwave plasma has the characteristics of low energy, low damage, high activity and the like, and can greatly reduce the surface roughness, surface adsorbates and defects, thereby providing a high-quality growth surface; then, a phase change buffer layer is inserted between the upper and lower waveguide layers and the active layer to relieve lattice mismatch between the waveguide layers and the active layer strain superlattice, so that interface stress and defects are greatly reduced, and interface quality is improved; and finally, the thickness, the components, the strain, the doping and the interface of the strained superlattice of the active layer are accurately controlled by controlling the switching of the III-V family source of the molecular beam epitaxy. Finally, a high-quality active layer quantum cascade strain superlattice structure with thousands of layers of repeated periods, specific thickness, small thickness fluctuation, uniform components, no overall stress, uniform doping, steep interface, low roughness and low defect density and a high-quality laser chip epitaxial layer structure are successfully grown on the InP substrate, and higher laser output power is obtained. The idea and method adopted by the invention are also applicable to other III-V group and II-VI group compound semiconductor photoelectric materials and devices.

Drawings

FIG. 1 is a schematic diagram of an epitaxial layer structure of a quantum cascade laser chip on an InP substrate;

FIG. 2 is a flow chart of a method for fabricating an epitaxial layer structure of a quantum cascade laser chip on an InP substrate;

FIG. 3a is a single-layer InAlAs Secondary Ion Mass Spectrometry (SIMS) test curve diagram of an epitaxial layer structure and a manufacturing method of a quantum cascade laser chip on an InP substrate;

FIG. 3b is a single-layer InGaAs Secondary Ion Mass Spectrometry (SIMS) test graph of the epitaxial layer structure and the manufacturing method of the quantum cascade laser chip on the InP substrate;

FIG. 4a is an Atomic Force Microscope (AFM) profile of the surface of a lower waveguide untreated with the epitaxial layer structure and fabrication method of a quantum cascade laser chip on an InP substrate;

FIG. 4b is an Atomic Force Microscope (AFM) profile of a quantum cascade laser chip epitaxial layer structure on an InP substrate and a lower waveguide surface processed by ECR plasma according to a manufacturing method;

FIG. 5 is a high resolution X-ray diffraction pattern (HRXRD) of a quantum cascade InGaAs/InAlAs strained superlattice structure on an InP substrate and a method of fabricating the same;

FIG. 6 is a High Resolution Transmission Electron Microscope (HRTEM) morphology of a quantum cascade laser chip epitaxial layer structure on an InP substrate and a manufacturing method quantum cascade InGaAs/InAlAs strained superlattice structure;

FIG. 7 is an optical image quality inspection result of a quantum cascade laser chip epitaxial layer wafer on an InP substrate and a manufacturing method thereof;

fig. 8 is a current density-output power characteristic curve diagram of a quantum cascade laser chip epitaxial layer structure on an InP substrate and a manufacturing method thereof, which are manufactured by the method of the present invention and the conventional growth method, respectively.

Reference numerals:

1. a substrate; 2. a lower waveguide layer; 3. a lower phase change buffer layer; 4. an active layer; 5. an upper phase change buffer layer; 6. an upper waveguide layer; 7. and a contact layer.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments.

Example 1

As shown in fig. 1, an epitaxial layer structure of a quantum cascade laser chip on an InP substrate comprises, from bottom to top: the waveguide structure comprises a substrate 1, a lower waveguide layer 2, a lower phase-change buffer layer 3, an active layer 4, an upper phase-change buffer layer 5, an upper waveguide layer 6 and a contact layer 7.

Wherein the substrate is InP material doped with n-type Si with a doping concentration of 1 × 10 ¹⁷ ～1×10 ¹⁸ cm ^-3 ；

Wherein the lower phase-change buffer layer is In _1-x Ga _x As and/or In _1-y Al _y A plurality of component gradient alloy layers formed by one or a combination of As, wherein the value of x is related to the component of the strain InGaAs alloy of the active layer and is more than or equal to 0 and less than or equal to 0.47, the component gradient change value delta x in the phase change buffer layer is 0.01 to 0.05, the value of y is related to the component of the strain InAlAs alloy of the active layer and is more than or equal to 0.48 and less than or equal to 1, and the component in the phase change buffer layer isThe gradient change value delta y is 0.01-0.05, the thickness of each layer is 1-10 nm, each layer is doped with n-type Si, and the doping concentration is 1 multiplied by 10 ¹⁶ ～5×10 ¹⁶ cm ^-3 . Fig. 2 gives examples of three phase change buffer layers.

Wherein the upper phase change buffer layer is In _1-x Ga _x As and/or In _1-y Al _y A plurality of component gradient alloy layers formed by one or a combination of As materials, wherein the material characteristics are similar to those of the lower phase-change buffer layer;

Wherein the contact layer is InP and/or InGaAs material lattice-matched with the substrate, the layer thickness is 0.1-1 μm, the contact layer is doped with n-type Si, and the doping concentration is 1 × 10 ¹⁸ ～8×10 ¹⁸ cm ^-3 ；

Specific examples are shown in table 1:

TABLE 1

TABLE 2

TABLE 3

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In this embodiment, the transition buffer layer is varied from a critical point of lattice matching with InP, such as In _0.53 Ga _0.47 As starts, and gradually approaches the value of the strained layer of the superlattice of the active layer 4 from the upper and lower directions, e.g. In _0.60 Ga _0.40 As。

In addition, the phase change buffer layer may be In _1-x Ga _x As, may be In _1-y Al _y As, in may be used _1-x Ga _x As/In _1- _y Al _y An As bilayer.

The lower phase-change buffer layer 3 is strain-transitioned from being lattice-mismatched with the substrate 1 to being lattice-matched with the InP of the substrate 1, and the upper phase-change buffer layer 4 is strain-transitioned from being lattice-mismatched with the substrate 1 to being lattice-matched with the InP of the substrate 1.

Example 2

As shown in fig. 2, a process flow diagram of an epitaxial layer structure of a quantum cascade laser chip on an InP substrate and a method for fabricating the same includes the following steps:

(a) InP wafers are immersed in boiled electronic pure acetone solvent and absolute ethyl alcohol solvent in sequence for ultrasonic cleaning, and the cleaning is carried out for 1-3 times and 1-5 min each time. Then, leaching the InP wafer for several times by using deionized water;

(c) Taking out the InP wafer in the substep (b), and drying in a vacuum drying oven at 100-150 ℃ for 0.5-1 h;

and 2, growing a lower waveguide layer on the InP wafer subjected to the chemical cleaning in the last step by adopting Molecular Beam Epitaxy (MBE) or Metal Organic Chemical Vapor Deposition (MOCVD). Firstly, the wafer needs to be dehydrated and degassed in a pretreatment chamber, the pretreatment temperature is 100-200 ℃, and the pretreatment time is 1-2 h. After the pretreatment is finished, the wafer is conveyed to a growth chamber to carry out epitaxial growth of a lower waveguide layer, wherein the growth temperature of MBE is 450-550 ℃, and the growth temperature of MOCVD is 600-760 ℃;

and 3, putting the wafer on which the lower waveguide is grown in the previous step into a sample tray, and pushing the wafer into a discharge chamber of an ECR microwave plasma system through a sample feeding rod. Then, the mechanical pump and the molecular pump are started to perform vacuum treatment in sequence, and when the vacuum degree reaches 10 ^-6 Heating and raising the temperature when the pressure is lower than Pa, and carrying out dehydration and degassing pretreatment on the wafer, wherein the pretreatment temperature is 100-200 ℃, and the pretreatment time is 1-2 h. After the pretreatment is finished, setting the temperature to be required, introducing a plasma excitation gas source, and starting the ECR microwave plasma surface treatment. The exciting gas source of the electron cyclotron resonance microwave plasma is H ₂ Mixed gas of/Ar, H ₂ The volume ratio in the mixed gas is 0.1-5%, the total mixing flow is 20-60 sccm, the microwave power is 300-800W, the treatment temperature is 200-400 ℃, and the treatment time is 1-20 min;

and 4, growing a phase-change buffer layer on the wafer subjected to the ECR plasma surface treatment in the last step by adopting Molecular Beam Epitaxy (MBE). Firstly, the wafer is conveyed to a pretreatment chamber for degassing and dehydration treatment, the pretreatment temperature is 100-200 ℃, and the pretreatment time is 1-2 h. After the pretreatment is finished, the wafer is conveyed to a growth chamber to carry out epitaxial growth of a lower phase-change buffer layer, the growth temperature is 450-550 ℃, the growth rate is 0.1-1 nm/s, the beam current ratio of the V group/III group elements is 5-25, the rotation speed of a substrate during growth is 5-15 r/min, the switching of a shutter of a III group source furnace can be related during the growth of the lower phase-change buffer layer, and the specific switching mode refers to step 5;

(a) When switching from the InGaAs layer to the InAlAs layer, firstly, closing the shutters of the In source furnace and the Ga source furnace In the previous step; secondly, the shutter of the As source furnace is normally opened, the vacuum pump pumps away the residual In and Ga sources In the previous step, and the III-group source is interrupted for 0-5 s; finally, simultaneously opening shutters of an In source furnace and an Al source furnace to grow InAlAs;

step 9, finishing the quantum cascade laser manufacturing on the epitaxial wafer prepared in the previous step, including depositing SiO ₂ The manufacturing method comprises the following process steps of photoetching to determine ridge waveguide, corrosion, secondary epitaxial InP, photoetching to determine an electrode window, substrate thinning, electrode manufacturing, cleavage, film coating, flip chip welding, gold wire ball bonding and packaging.

In order to illustrate the technical advantages of the invention by comparison, a comparison sample which is not subjected to ECR microwave plasma surface treatment, does not have a growth phase change buffer layer and adopts a conventional molecular beam epitaxy source furnace switching step, namely a sample prepared by a conventional growth method is prepared.

The following further describes the present invention according to the actual measurement content and the actual measurement result:

FIGS. 3 a-3 b are graphs of Secondary Ion Mass Spectroscopy (SIMS) measurements of a single layer of InAlAs and (b) a single layer of InGaAs. Monolayer compositions and doping concentrations can be obtained by SIMS testing and the test results of fig. 3a show that the elemental ratio In the InAlAs for the monolayer: al =0.39: the doping concentration of 0.61, si is 1.4E17/cm ³ And meets the design requirements. The test results In fig. 3b show the element ratio In the single layer InGaAs: ga =0.6:0.4, the doping concentration of Si is 1.35E17/cm ³ And also meets the design requirements. The content and distribution of the elements are stable through the depth profile curve of the elements, which shows that the components are uniform and have small fluctuation. Growth experiments of single-layer InAlAs and InGaAs are used for calibrating various growth parameters of MBE, and a foundation is laid for later growth of strain superlattice.

FIGS. 4a and 4b are Atomic Force Microscope (AFM) topographical views of an untreated lower waveguide surface and an ECR microwave plasma treated lower waveguide surface. The root mean square roughness of the surface of the grown waveguide without any treatment was 0.16nm as obtained from the AFM test of fig. 4 a; from the AFM test of FIG. 4b, it can be obtained that the root mean square roughness of the surface of the lower waveguide after the growth of the lower waveguide is completed and after the ECR microwave plasma treatment is performed, is 0.11nm, and the result shows that the ECR plasma treatment of the present invention can greatly reduce the surface roughness, surface adsorbates and defects, thereby providing a good quality growth surface.

FIG. 5 is a high resolution X-ray diffraction pattern (HRXRD) of a quantum cascade InGaAs/InAlAs strained superlattice structure grown by the method of the present invention. Firstly, as can be seen from the swing curve of the obtained InGaAs/InAlAs strain superlattice, multi-stage satellite peaks appear on two sides of the main peak InP substrate peak, which indicates that a complete periodic structure appears, and the superlattice structure is successfully prepared. Secondly, the number of satellite peaks is large and the intensity is large, reflecting that the quality of the grown superlattice is good. In addition, the satellite peaks were all sharp and the full width at half maximum (FWHM) was very narrow, indicating that the interface roughness was low and the interface quality in the superlattice was high, again confirming that the crystal quality of the superlattice was perfect. Finally, compared with the situation that the difference between the zero-order diffraction peak and the substrate InP diffraction peak is large in other patent documents, the zero-order diffraction peak obtained by the method almost coincides with the substrate InP diffraction peak, the fact that the net stress of the whole superlattice is zero is shown, and a perfect quantum cascade strain superlattice structure of a strain compensation system is obtained. The above analysis shows that the quantum cascade InGaAs/InAlAs strain superlattice structure grown by the invention has perfect interface and crystal quality, which shows that the ECR microwave plasma surface treatment technology, the phase change buffer layer and the molecular beam epitaxy source furnace switching technology adopted by the invention are useful and have good effect, the superlattice quality can be improved, and the parameters of superlattice components, thickness, strain, interface and the like can be accurately controlled.

FIG. 6 is a High Resolution Transmission Electron Microscope (HRTEM) morphology of quantum cascade InGaAs/InAlAs strained superlattice structure grown by the method of the present invention. HRTEM tests show that the thickness of the prepared superlattice meets the requirements, the volatility is small, the heterogeneous interface is straight and steep, and the thickness is further verified to be compatible with the data of a high-resolution X-ray diffraction pattern in FIG. 5, which shows that the quantum cascade InGaAs/InAlAs strain superlattice structure grown by the method has perfect interface and crystal quality, and the technical scheme adopted by the method is proved to be useful and have good effect.

FIG. 7 shows the result of optical image quality inspection of the surface of the epitaxial layer wafer of the quantum cascade laser chip prepared by the method of the present invention. The actual measurement result shows that the defect density of the surface of the quantum cascade laser chip epitaxial layer wafer is 108/cm ² The method has low defect density, and further proves that the epitaxial layer of the quantum cascade laser prepared by the method has good crystal quality, and reflects the technical scheme adopted by the invention to be useful and have good effect.

Fig. 8 is a graph of current density-output power characteristics of a quantum cascade laser fabricated using the method of the present invention and a conventional growth method, respectively. The actual measurement result shows that the output light power of the quantum cascade laser manufactured by the method can reach 270mW under the working condition of 20 ℃ and continuous waves, and the central wavelength of the laser is about 8 mu m; in contrast, the output optical power of the quantum cascade laser manufactured by the conventional growth method is only 80 mW under the same test working condition, which shows that the output characteristic of the laser can be greatly improved by adopting the method of the invention, and higher device output power is obtained. The improvement in output power is attributed to the ability of the inventive method to achieve high quality active layer strained superlattice and epitaxial layer quality.

The actual measurement result shows that the invention has the advantages that: compared with the prior art, the invention firstly utilizes the surface treatment technology of the electron cyclotron resonance microwave plasma to treat the surface of a lower waveguide layer, the electron cyclotron resonance microwave plasma has the characteristics of low energy, low damage, high activity and the like, and can greatly reduce the surface roughness, surface adsorbates and defects, thereby providing a high-quality growth surface; then, a phase change buffer layer is inserted between the upper and lower waveguide layers and the active layer to relieve lattice mismatch between the waveguide layers and the active layer strain superlattice, so that interface stress and defects are greatly reduced, and the interface quality is improved; and finally, the thickness, the components, the strain, the doping and the interface of the strained superlattice of the active layer are accurately controlled by controlling the switching of the III-V family source of the molecular beam epitaxy. Finally, a high-quality active layer quantum cascade strain superlattice structure with thousands of layers of repeated periods, specific thickness, small thickness fluctuation, uniform components, no overall stress, uniform doping, steep interface, low roughness and low defect density and a high-quality laser chip epitaxial layer structure are successfully grown on the InP substrate, and higher laser output power is obtained. The idea and method adopted by the invention are also applicable to other III-V group and II-VI group compound semiconductor photoelectric materials and devices.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered as the technical solutions and the inventive concepts of the present invention within the technical scope of the present invention.

Claims

1. An epitaxial layer structure of a quantum cascade laser chip on an InP substrate is characterized in that: the active layer is of a strain superlattice structure, a phase change buffer layer is arranged between the active layer and the substrate and used for adjusting lattices between the substrate and the active layer, and the phase change buffer layer is a multilayer component gradient alloy layer.

2. The epitaxial layer structure of a quantum cascade laser chip on an InP substrate of claim 1, wherein: the waveguide structure comprises a substrate (1), a lower waveguide layer (2), a lower phase-change buffer layer (3), an active layer (4), an upper phase-change buffer layer (5), an upper waveguide layer (6) and a contact layer (7) which are sequentially connected from bottom to top;

the phase change buffer layer comprises the lower phase change buffer layer (3) and the upper phase change buffer layer (5), the lower phase change buffer layer (3) relieves the lattice mismatch between the strained superlattices of the lower waveguide layer (2) and the active layer (4), and the upper phase change buffer layer (5) relieves the lattice mismatch between the strained superlattices of the active layer (4) and the upper waveguide layer (4);

carrying out surface treatment on the lower waveguide layer (2) by using electron cyclotron resonance microwave plasma, and then growing by using Molecular Beam Epitaxy (MBE) to obtain the lower phase-change buffer layer (3);

the active layer (4) is of a strained superlattice structure.

3. The epitaxial layer structure of a quantum cascade laser chip on an InP substrate of claim 2, wherein: the substrate (1) is an InP wafer, and the substrate (1) has a doping concentration of 1 × 10 ¹⁷ ～1×10 ¹⁸ cm ^-3 Doping n-type Si;

the lower waveguide layer (2) is InP and/or InGaAs material lattice-matched with the substrate (1), and the lower waveguide layer (2) has doping concentration of 1 × 10 ¹⁶ ～5×10 ¹⁶ cm ^-3 The layer thickness of the lower waveguide layer (2) is 1-4 μm;

the active layer (4) is In _1-x Ga _x As、In _1-y Al _y As repeats strain superlattice structure composed of 100-500 periods, the layer thickness of the active layer (4) is 0.5-6.5 nm, and partial layers of the active layer (4) have doping concentration of 1 × 10 ¹⁷ ～5×10 ¹⁷ cm ^-3 The n-type Si is doped, x is more than or equal to 0 and less than 0.47, and y is more than 0.48 and less than or equal to 1;

the upper waveguide layer (6) is made of InP and/or InGaAs lattice-matched with the substrate (1), and the upper waveguide layer (6) has a doping concentration of 1 × 10 ¹⁶ ～1×10 ¹⁷ cm ^-3 The thickness of the upper waveguide layer (6) is 1-5 μm;

the contact layer (7) is InP and/or InGaAs material lattice-matched with the substrate (1), and the contact layer (7) has a doping concentration of 1 × 10 ¹⁸ ～8×10 ¹⁸ cm ^-3 The contact layer (7) has a layer thickness of 0.1 to 1 μm.

4. The epitaxial layer structure of a quantum cascade laser chip on an InP substrate of claim 2, wherein: the lower phase-change buffer layer (3) transitions from a matching regime with the substrate (1) to a strained regime of the active layer (4), and the upper phase-change buffer layer (5) transitions from the strained regime of the active layer (4) to a matching regime of the upper waveguide layer (6).

5. The epitaxial layer structure of an InP-substrate quantum cascade laser chip of claim 4, wherein:

the lower phase change buffer layer (3) is In _1-x Ga _x As and/or In _1-y Al _y A multi-layer component gradient alloy layer formed by one or a combination of As, x is more than or equal to 0 and less than or equal to 0.47, y is more than or equal to 0.48 and less than or equal to 1 _1-x Ga _x The gradient change value Deltax of As component is 0.01-0.05 _1-y Al _y The gradient change value delta y of the As component is 0.01-0.05, the thickness of each layer of the lower phase change buffer layer (3) is 1-10 nm, and the doping concentration of partial layers is 1 multiplied by 10 ¹⁶ ～5×10 ¹⁶ cm ^-3 Doping n-type Si;

the upper phase change buffer layer (5) is In _1-x Ga _x As and/or In _1-y Al _y A plurality of component gradient alloy layers formed by one or a combination of As, x is more than or equal to 0 and less than or equal to 0.47, y is more than or equal to 0.48 and less than or equal to 1 _1-x Ga _x The gradient change value Deltax of As component is 0.01-0.05 _1-y Al _y The gradient change value delta y of the As component is 0.01-0.05, the thickness of each layer of the lower phase change buffer layer (3) is 1-10 nm, and the doping concentration of partial layers is 1 multiplied by 10 ¹⁶ ～5×10 ¹⁶ cm ^-3 Is doped with n-type Si.

6. A manufacturing method of an epitaxial layer structure of a quantum cascade laser chip on an InP substrate is characterized in that: the method comprises the following steps:

s1, cleaning a substrate (1);

s2, growing a lower waveguide layer (2);

s3, carrying out surface treatment on the lower waveguide layer (2) by using an Electron Cyclotron Resonance (ECR) microwave plasma system;

s4, growing a phase change buffer layer (3);

s5, growing an active layer (4) and obtaining a quantum cascade strain superlattice;

s6, growing a phase change buffer layer (5);

s7, growing an upper waveguide layer (6);

and S8, growing a contact layer (7) to obtain the epitaxial layer structure of the laser chip.

7. The method of claim 6, wherein the epitaxial layer structure of the quantum cascade laser chip on the InP substrate comprises: step S1 is to chemically clean the substrate (1), the step S1 comprising:

s11, sequentially immersing the substrate (1) in a boiled electronic pure acetone solvent and an absolute ethyl alcohol solvent for ultrasonic cleaning, wherein the cleaning is carried out for 1-3 times and 1-5 min each time; then, leaching the substrate (1) with deionized water at least twice, wherein the substrate (1) is an InP wafer;

s12, taking out the substrate (1) in the step S11, placing the substrate in a mixed solution composed of concentrated sulfuric acid, hydrogen peroxide and water according to a volume ratio of 5; subsequently, rinsing the substrate (1) at least twice with deionized water;

s13, taking out the substrate (1) in the step S12, and drying the substrate in a vacuum drying oven at 100-150 ℃ for 0.5-1 h to obtain a cleaned substrate;

in the step S2, growing the lower waveguide layer (2) on the cleaned substrate by using Molecular Beam Epitaxy (MBE) or Metal Organic Chemical Vapor Deposition (MOCVD);

the cleaned substrate is subjected to dehydration and degassing treatment in a pretreatment chamber, the pretreatment temperature is 100-200 ℃, and the pretreatment time is 1-2 h; after the pretreatment is finished, the substrate (1) is conveyed to a growth chamber to carry out epitaxial growth on the lower waveguide layer (2), the growth temperature of MBE is 450-550 ℃, and the growth temperature of MOCVD is 600-760 ℃;

the method further comprises the step S9 of manufacturing a laser on the epitaxial layer structure of the laser chip to obtain the laser;

quantum cascade laser manufacturing is carried out on the epitaxial layer structure of the laser chip, and the quantum cascade laser manufacturing comprises deposition of SiO ₂ And photolithographyDetermining ridge waveguide, corroding, extending InP for the second time, photoetching to determine an electrode window, thinning a substrate, manufacturing an electrode, cleaving, coating a film, performing flip chip bonding, performing gold wire ball bonding, packaging, and then obtaining the laser.

8. The method of claim 6, wherein the epitaxial layer structure of the quantum cascade laser chip on the InP substrate comprises:

step S3 includes the following steps:

s31, putting the wafer with the waveguide grown in the step S2 into a sample tray, and pushing the wafer into a discharge chamber of the ECR microwave plasma system through a sample sending rod;

s32, sequentially opening the mechanical pump and the molecular pump for vacuum treatment, and when the vacuum degree reaches 10 ^-6 Heating when the pressure is lower than Pa, and carrying out dehydration and degassing pretreatment on the wafer at the pretreatment temperature of 100-200 ℃ for 1-2 h;

9. The method of claim 6, wherein the epitaxial layer structure of the quantum cascade laser chip on the InP substrate is formed by:

in step S4, growing the lower phase-change buffer layer (3) on the wafer subjected to the ECR microwave plasma surface treatment in the step S3 by using Molecular Beam Epitaxy (MBE);

firstly, conveying a wafer to a pretreatment chamber for degassing and dehydrating treatment, wherein the pretreatment temperature is 100-200 ℃, and the pretreatment time is 1-2 h; after the pretreatment is finished, the wafer is conveyed to a growth chamber to carry out phase-change buffer layer under epitaxial growth, the growth temperature is 450-550 ℃, the growth rate is 0.1-1 nm/s, the beam current ratio of V group/III group elements is 5-25, and the rotation speed of the substrate (1) is 5-15 r/min during growth;

in the step S5, on the wafer of the phase-change buffer layer after the growth in the step S4, continuously growing the active layer (4) by using Molecular Beam Epitaxy (MBE), wherein the active layer (4) is a quantum cascade strain superlattice, the growth temperature is 450-550 ℃, the growth rate is 0.1-1 nm/S, the beam current ratio of the V group/III group elements is 5-25, and the rotation speed of the wafer is 5-15 r/min during growth;

in step S6, continuously growing the upper phase-change buffer layer (5) on the wafer of which the quantum cascade strain superlattice of the active layer is grown in the step S5 by using molecular beam epitaxy MBE, wherein the growth temperature is 450-550 ℃, the growth rate is 0.1-1 nm/S, the beam current ratio of the V group element to the III group element is 5-25, and the rotation speed of the substrate is 5-15 revolutions per minute during growth;

in the step S7, growing the upper waveguide layer (6) on the wafer on which the upper phase-change buffer layer (5) is grown in the step S6 by using Molecular Beam Epitaxy (MBE) or Metal Organic Chemical Vapor Deposition (MOCVD), wherein the growth temperature of the MBE is 450-550 ℃, and the growth temperature of the MOCVD is 600-760 ℃;

in step S8, growing the contact layer (7) on the wafer with the upper waveguide layer (6) grown in step S7 by using Molecular Beam Epitaxy (MBE) or Metal Organic Chemical Vapor Deposition (MOCVD), wherein the growth temperature of the Molecular Beam Epitaxy (MBE) is 450-550 ℃, and the growth temperature of the Metal Organic Chemical Vapor Deposition (MOCVD) is 600-760 ℃.

10. The method of claim 6, wherein the epitaxial layer structure of the quantum cascade laser chip on the InP substrate comprises:

the step S5 comprises the switching of the shutter of the III-family source furnace, and the specific switching mode comprises the following steps:

in the step S7, when MBE is used for growth and the material of the upper waveguide layer (6) is InP, a V-family source furnace shutter is switched;

the switching method comprises the following steps: when switching from an InGaAs layer or an InAlAs layer to an InP layer, firstly, closing the shutter of the In source furnace, the Ga source or the Al source furnace In the previous step; secondly, continuously opening an As source furnace shutter, and pumping residual In and Ga (Al) sources In the previous step away by a vacuum pump; then, closing the As source furnace shutter and simultaneously rapidly opening the P source furnace shutter, and pumping away the residual As source in the previous step by a vacuum pump; finally, opening an In source furnace shutter to grow InP;

in the step S8, when MBE is used for growth and the material of the contact layer (7) is InGaAs, switching of a shutter is carried out by a V-group source furnace;

the switching method comprises the following steps: when the InP layer is switched to the InGaAs layer, firstly, the shutter of the In source furnace In the previous step is closed; secondly, continuously opening a P source furnace shutter, and pumping away the residual In source In the previous step by a vacuum pump; then, closing the shutter of the P source furnace, simultaneously and rapidly opening the shutter of the As source furnace, and pumping the residual P source in the previous step away by a vacuum pump; and finally, simultaneously opening an In source furnace shutter and a Ga source furnace shutter to grow the InGaAs.