US20090086785A1 - Semiconductor light emitting device and method for manufacturing the same - Google Patents

Semiconductor light emitting device and method for manufacturing the same Download PDF

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Publication number
US20090086785A1
US20090086785A1 US12/199,507 US19950708A US2009086785A1 US 20090086785 A1 US20090086785 A1 US 20090086785A1 US 19950708 A US19950708 A US 19950708A US 2009086785 A1 US2009086785 A1 US 2009086785A1
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layer
gaas
light emitting
emitting device
quantum dot
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Nobuaki Hatori
Tsuyoshi Yamamoto
Manabu Matsuda
Yasuhiko Arakawa
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Fujitsu Ltd
University of Tokyo NUC
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Fujitsu Ltd
University of Tokyo NUC
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Assigned to FUJITSU LIMITED, THE UNIVERSITY OF TOKYO reassignment FUJITSU LIMITED ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: ARAKAWA, YASUHIKO, YAMAMOTO, TSUYOSHI, HATORI, NOBUAKI, MATSUDA, MANABU
Publication of US20090086785A1 publication Critical patent/US20090086785A1/en
Priority to US13/898,808 priority Critical patent/US8906721B2/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/30—Structure or shape of the active region; Materials used for the active region
    • H01S5/34—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers
    • H01S5/341—Structures having reduced dimensionality, e.g. quantum wires
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y20/00—Nanooptics, e.g. quantum optics or photonic crystals
    • H—ELECTRICITY
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    • H01S5/00—Semiconductor lasers
    • H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
    • H01S5/12—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region the resonator having a periodic structure, e.g. in distributed feedback [DFB] lasers
    • H—ELECTRICITY
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    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/20—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers
    • H01S5/22—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers having a ridge or stripe structure
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
    • H01L33/26—Materials of the light emitting region
    • H01L33/30—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table
    • H—ELECTRICITY
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    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/04—Processes or apparatus for excitation, e.g. pumping, e.g. by electron beams
    • H01S5/042—Electrical excitation ; Circuits therefor
    • H01S5/0421—Electrical excitation ; Circuits therefor characterised by the semiconducting contacting layers
    • H01S5/0422—Electrical excitation ; Circuits therefor characterised by the semiconducting contacting layers with n- and p-contacts on the same side of the active layer
    • H01S5/0424—Electrical excitation ; Circuits therefor characterised by the semiconducting contacting layers with n- and p-contacts on the same side of the active layer lateral current injection
    • H—ELECTRICITY
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    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/04—Processes or apparatus for excitation, e.g. pumping, e.g. by electron beams
    • H01S5/042—Electrical excitation ; Circuits therefor
    • H01S5/0425—Electrodes, e.g. characterised by the structure
    • H01S5/04256—Electrodes, e.g. characterised by the structure characterised by the configuration
    • H01S5/04257—Electrodes, e.g. characterised by the structure characterised by the configuration having positive and negative electrodes on the same side of the substrate
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/20—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers
    • H01S5/22—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers having a ridge or stripe structure
    • H01S5/2205—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers having a ridge or stripe structure comprising special burying or current confinement layers
    • H01S5/2206—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers having a ridge or stripe structure comprising special burying or current confinement layers based on III-V materials
    • H01S5/221—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers having a ridge or stripe structure comprising special burying or current confinement layers based on III-V materials containing aluminium
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/30—Structure or shape of the active region; Materials used for the active region
    • H01S5/305—Structure or shape of the active region; Materials used for the active region characterised by the doping materials used in the laser structure
    • H01S5/3086—Structure or shape of the active region; Materials used for the active region characterised by the doping materials used in the laser structure doping of the active layer
    • H01S5/309—Structure or shape of the active region; Materials used for the active region characterised by the doping materials used in the laser structure doping of the active layer doping of barrier layers that confine charge carriers in the laser structure, e.g. the barriers in a quantum well structure
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/30—Structure or shape of the active region; Materials used for the active region
    • H01S5/34—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers
    • H01S5/3403—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers having a strained layer structure in which the strain performs a special function, e.g. general strain effects, strain versus polarisation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/30—Structure or shape of the active region; Materials used for the active region
    • H01S5/34—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers
    • H01S5/341—Structures having reduced dimensionality, e.g. quantum wires
    • H01S5/3412—Structures having reduced dimensionality, e.g. quantum wires quantum box or quantum dash
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/30—Structure or shape of the active region; Materials used for the active region
    • H01S5/34—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers
    • H01S5/343—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser
    • H01S5/34313—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser with a well layer having only As as V-compound, e.g. AlGaAs, InGaAs
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S977/00—Nanotechnology
    • Y10S977/70—Nanostructure
    • Y10S977/773—Nanoparticle, i.e. structure having three dimensions of 100 nm or less
    • Y10S977/774—Exhibiting three-dimensional carrier confinement, e.g. quantum dots

Definitions

  • This invention relates to a semiconductor light emitting device used as a light source for optical fiber communication, for example, and a method for manufacturing the semiconductor light emitting device, and specifically relates to a semiconductor light emitting device, which is formed on a GaAs substrate and has quantum dots in an active layer, and a method for manufacturing the semiconductor light emitting device.
  • a method for manufacturing a DFB laser there is widely used a method of growing crystal until an intermediate layer in a layer structure of a laser, forming a diffraction grating by patterning etching, and thereafter growing again the remaining layer in the layer structure of the laser.
  • a semiconductor light emitting device including a GaAs substrate, a quantum dot active layer formed over the GaAs substrate, a GaAs layer formed above or below the quantum dot active layer, and a diffraction grating formed from InGaP or InGaAsP and periodically provided along an propagating direction of light in the GaAs layer.
  • FIG. 1 is a schematic cross sectional view showing a structure along an propagating direction of light of a semiconductor light emitting device (quantum dot DFB laser) according to a first embodiment
  • FIG. 2 is a schematic cross sectional view showing a structure along a direction crosswise to the propagating direction of light of the semiconductor light emitting device (quantum dot DFB laser) according to the first embodiment;
  • FIGS. 3(A) to 3(C) are schematic cross sectional views for explaining a method for manufacturing the semiconductor light emitting device (quantum dot DFB laser) according to the first embodiment;
  • FIG. 4 is a schematic cross sectional view showing a structure along the propagating direction of light of a semiconductor light emitting device (quantum dot DFB laser) according to a modification of the first embodiment;
  • FIG. 5 is a schematic cross sectional view showing a structure along an propagating direction of light of a semiconductor light emitting device (quantum dot DFB laser) according to a second embodiment
  • FIG. 6 is a schematic cross sectional view showing a structure along a direction crosswise to the propagating direction of light of the semiconductor light emitting device (quantum dot DFB laser) according to the second embodiment;
  • FIG. 7 is a schematic cross sectional view showing a structure along an propagating direction of light of a semiconductor light emitting device (quantum dot DFB laser) according to a third embodiment
  • FIG. 8 is a schematic cross sectional view showing a structure along a direction crosswise to the propagating direction of light of the semiconductor light emitting device (quantum dot DFB laser) according to the third embodiment;
  • FIGS. 9(A) and 9(B) are schematic cross sectional views showing a structure along a direction crosswise to the propagating direction of light of the semiconductor light emitting device (quantum dot DFB laser) according to a modification of the third embodiment.
  • FIG. 10 is a schematic cross sectional view showing a constitution of a semiconductor light emitting device (quantum dot DFB laser) according to a modification of each embodiment.
  • the semiconductor light emitting device is formed on a GaAs substrate and has a quantum dot active layer and a diffraction grating (index coupled semiconductor light emitting device using quantum dot; index coupled DFB laser using quantum dot in this embodiment). As shown in FIG.
  • the semiconductor light emitting device is provided with a p-type GaAs substrate (p-type conductive substrate) 1 , a p-type AlGaAs lower cladding layer 2 formed over the p-type GaAs substrate 1 , a quantum dot active layer 3 formed over the p-type AlGaAs lower cladding layer 2 , an n-type GaAs guide layer (n-type GaAs layer) 4 formed over the quantum dot active layer 3 , an n-type AlGaAs upper cladding layer 5 formed over the n-type GaAs guide layer 4 , and an n-type GaAs contact layer 6 formed over the n-type AlGaAs upper cladding layer 5 .
  • the quantum dot semiconductor light emitting device in this embodiment has a stacked structure in which the p-type AlGaAs lower cladding layer 2 , the quantum dot active layer 3 , the n-type GaAs guide layer 4 including an n-type InGaP diffraction grating 7 , the n-type AlGaAs upper cladding layer 5 , and the n-type GaAs contact layer 6 are sequentially stacked on the p-type GaAs substrate 1 .
  • the GaAs guide layer 4 includes the narrow line-shaped InGaP diffraction grating 7 which is formed from InGaP lattice-matched to GaAs and periodically provided along an propagating direction of light.
  • the DFB laser As an example of a method for manufacturing the DFB laser which is formed over the GaAs substrate and has a quantum well active layer, there is a method of etching an AlGaAs layer to form a diffraction grating, and, thus, to bury the diffraction grating with the GaAs layer (hereinafter referred to as first technique).
  • quantum dots DFB laser index coupled DFB laser using quantum dot
  • quantum dots DFB laser loss coupled DFB laser using quantum dot
  • the AlGaAs layer is etched to form the diffraction grating, in the etching, the AlGaAs layer is exposed to be oxidized, whereby an oxide is formed on the surface of the AlGaAs layer.
  • the diffraction grating formed by the AlGaAs layer cannot be buried with the GaAs layer.
  • quantum dots having a property unstable to a temperature is thermally deteriorated or degraded due to the high temperature process.
  • the emission spectrum becomes not discrete. Therefore, the quantum dot laser cannot be manufactured by using the material and method used in the first technique.
  • the threshold current (the threshold value) is easily raised.
  • the diffraction grating can be formed in the semiconductor stacked structure, and, at the same time, it is also desirable that the transverse mode (fundamental mode) can be easily controlled, whereby a sufficient coupling constant can be obtained. Therefore, since higher-order transverse modes can be suppressed, the width of the ridge can be widen, thereby the resistance can be reduced.
  • the diffraction grating can be formed in the semiconductor stacked structure while preventing the quantum dot from being thermally deteriorated or degraded.
  • this embodiment provides the above constitution.
  • the diffraction grating is formed from InGaP, and it is difficult to form the oxide on the surface in the etching, and therefore, the InGaP diffraction grating 7 can be buried with the GaAs guide layer 4 , whereby the diffraction grating 7 can be formed in the semiconductor stacked structure.
  • the InGaP diffraction grating 7 is buried with the GaAs guide layer 4 , and a semiconductor material not containing Al is used, whereby it is difficult to form an oxide on the surface in the etching for the formation of the diffraction grating 7 . Therefore, the high temperature process (high temperature processing) for removing the oxide is not required to be performed, whereby the processes after the formation of the quantum dot active layer 3 can be performed at a temperature lower than a temperature at which the quantum dot is thermally deteriorated or degraded.
  • the quantum dot semiconductor light emitting device index coupled DFB laser using quantum dot
  • the quantum dot semiconductor light emitting device having the diffraction grating 7 in the semiconductor stacked structure can be manufactured without thermally deteriorating or thermally degrading the quantum dot.
  • the InGaP diffraction grating 7 in the GaAs guide layer 4 is formed in a narrow line-shape, there is no GaAs/InGaP hetero-interface in the DFB laser which is formed on the GaAs substrate disclosed in Japanese Patent Application Laid-Open No. HEI 7-263802. Thus, there is an effect of preventing increase of the device resistance.
  • the n-type GaAs guide layer 4 is provided between the quantum dot active layer 3 and the n-type AlGaAs upper cladding layer 5 .
  • the GaAs guide layer 4 including the InGaP diffraction grating 7 is provided on the n-type cladding layer side.
  • an electric current is less likely to flow in a semiconductor layer having a diffraction grating; however, in this embodiment, the diffraction grating is provided on the n-type cladding layer side through which electrons with small effective mass pass, whereby the resistance becomes smaller than in the case of providing the diffraction grating on the p-type cladding layer side through which holes with large effective mass pass.
  • the quantum dot semiconductor light emitting device in this embodiment is constituted as a ridge waveguide type quantum dot semiconductor light emitting device (ridge waveguide type quantum dot DFB laser) having a ridge structure (stripe structure; stripe-shaped mesa structure) 8 including an n-type GaAs contact layer 6 , an n-type AlGaAs upper cladding layer 5 , and an n-type GaAs guide layer 4 .
  • ridge waveguide type quantum dot DFB laser having a ridge structure (stripe structure; stripe-shaped mesa structure) 8 including an n-type GaAs contact layer 6 , an n-type AlGaAs upper cladding layer 5 , and an n-type GaAs guide layer 4 .
  • the upper surface of the quantum dot active layer 3 is exposed on the opposite sides (both sides) of the ridge structure 8 . Namely, the quantum dot active layer 3 extends to the end face of the p-type GaAs substrate 1 .
  • the GaAs guide layer 4 including the InGaP diffraction grating 7 is removed, and the ridge structure 8 is formed so that the quantum dot active layer 3 is exposed, whereby the coupling constant of a transverse fundamental mode to the diffraction grating is increased, and there is an effect of suppressing higher-order transverse modes.
  • the quantum dot active layer 3 is an InAs quantum dot active layer containing in a part thereof p-type impurities and having the emission wavelength of 1.3 ⁇ m.
  • the quantum dot active layer 3 has a stacked structure in which a layer (quantum dot layer) composed of InAs quantum dots 10 , an i-InAs wetting layer 11 , an i-InGaAs strain relaxation layer (side barrier layer) 12 formed to cover the InAs quantum dots 10 , and a GaAs layer 13 (barrier layer; p-type doped layer; in this embodiment, the GaAs layer 13 is composed of an i-GaAs layer 14 , a p-GaAs layer 15 , and an i-GaAs layer 16 ) with the p-type impurities doped in a part thereof are repeatedly stacked a plurality of times (10 times in this embodiment) on the i-GaAs layer (barrier layer) 9 .
  • the constitution of the quantum dot active layer 3 is not limited to the above.
  • the quantum dot active layer 3 has the GaAs barrier layer 13 with the p-type impurities doped in a part thereof (that is, the GaAs barrier layer 13 includes the p-GaAs layer 15 )
  • the quantum dot active layer 3 may be constituted so that at least one of the quantum dots 10 , the wetting layer 11 , the barrier layers 9 and 13 , and the side barrier layer 12 which constitute the quantum dot active layer 3 is a layer (p-type quantum dot active layer) with the p-type impurities doped therein. Since the quantum dot active layer 3 is the p-type quantum dot active layer, the temperature characteristic of the device can be substantially improved, whereby the quantum dot semiconductor light emitting device (quantum dot DFB laser in this embodiment) with an excellent temperature characteristic can be realized.
  • the quantum dot active layer 3 is the p-type quantum dot active layer
  • the lower cladding layer 2 formed over the lower side of the quantum dot active layer 3 is formed from p-type AlGaAs
  • the upper cladding layer 5 included in the ridge structure 8 is formed from n-type AlGaAs, whereby the ridge structure (ridge waveguide) with a small area of p-n heterojunction can be formed, and, at the same time, the ridge waveguide type quantum dot semiconductor light emitting device with a small capacitance can be manufactured.
  • a structure in which, when the device length is 300 ⁇ m, an anti-reflection coating is applied to the front facet (end face) and a high reflection coating is applied to the back facet (end face), may be applied.
  • the method for manufacturing the semiconductor light emitting device includes forming the lower cladding layer 2 over the GaAs substrate 1 , forming the quantum dot active layer 3 over the lower cladding layer 2 , forming a first semiconductor layer 7 A over the quantum dot active layer 3 , forming the diffraction grating 7 by etching the first semiconductor layer 7 A, forming the guide layer (second semiconductor layer) 4 burying (covering) the diffraction grating 7 , forming the upper cladding layer 5 having an conductive type different from that of the lower cladding layer 2 over the guide layer 4 , and forming the contact layer 6 over the upper cladding layer 5 [see, FIGS. 1 and 3(A) to 3 (C)].
  • the processes after the process of forming the quantum dot active layer 3 are performed at a temperature not thermally deteriorating or degrading the quantum dots. This is because, when the quantum dots are thermally deteriorated or degraded, the emission wavelength of the quantum dots is shifted to the short wavelength side by about 100 nm from the emission wavelength before the deterioration or degradation, whereby it is necessary to prevent the emission wavelength of the quantum dots from being deviated from an intended emission wavelength.
  • the p-AlGaAs lower cladding layer 2 in this embodiment, p-Al 0.35 Ga 0.65 As lower cladding layer
  • the InAs quantum dot active layer 3 with the emission wavelength of 1.3 ⁇ m (a layer, which is composed of the InAs quantum dots 10 , the i-wetting layer 11 , and the i-InGaAs strain relaxation layer 12 , and the GaAs layer 13 with the p-type impurities doped in a part thereof are repeatedly stacked 10 times on the i-GaAs layer 9 to form the InAs quantum dot active layer 3 (see, FIG. 2 )) are sequentially stacked on the p-GaAs substrate (p-type conductive substrate) 1 by a molecular beam growth method (MBE method) for example (first growth).
  • MBE method molecular beam growth method
  • the processes after forming the InAs quantum dot active layer 3 that is, the following processes are performed at a temperature not thermally deteriorating or degrading the quantum dots (at a temperature not changing the emission wavelength and the emission intensity of the quantum dots).
  • the InAs quantum dots according to this embodiment is not thermally deteriorated or degraded at 630° C. or less. Namely, the emission wavelength of the InAs quantum dots is not changed at 630° C. or less (atmosphere temperature) (see, Denis Guimard et al., “High density InAs/GaAs quantum dots with enhanced photoluminescence intensity using antimony surfactant-mediated metal organic chemical vapor deposition”, APPLIED PHYSICS LETTERS 89, 183124 (2006)). Thus, the following processes are performed at 630° C.
  • the quantum dot semiconductor light emitting device (index coupled DFB laser using quantum dot) having the diffraction grating 7 in the semiconductor stacked structure can be manufactured without thermally deteriorating or degrading the InAs quantum dots.
  • the temperature at which the quantum dots are not thermally deteriorated or degraded is not more than 630° C.
  • the higher temperature can be set as the temperature not thermally deteriorating or degrading the quantum dots (temperature not changing the emission wavelength and the emission intensity of the quantum dots).
  • the n-InGaP layer 7 A and an n-GaAs layer 4 A are sequentially stacked on the InAs quantum dot active layer 3 at 600° C. for example by a metal organic chemical vapor deposition method (MOCVD method) for example (second growth).
  • MOCVD method metal organic chemical vapor deposition method
  • the SiO 2 film is formed over then-GaAs layer 4 A to form the diffraction grating pattern by the SiO 2 film 20 using an electron beam exposure method and an interference exposure method, for example.
  • an n-GaAs layer is subjected to selective etching using a sulfuric acid-based etchant, and an n-InGaP layer is subjected to selective etching using a hydrochloric acid-based etchant.
  • the narrow line-shaped n-InGaP diffraction grating 7 periodically provided along an propagating direction of light is formed.
  • An n-GaAs cap layer 4 B is formed over the n-InGaP diffraction grating 7 . In comparison with the case of forming the diffraction grating from the surface by etching, such a narrow line-shaped diffraction grating 7 can be easily formed.
  • the process of forming the n-GaAs layer 4 A over the n-InGaP layer 7 A is included after the process of forming the n-InGaP layer (first semiconductor layer) 7 A, and before forming the diffraction grating 7 [see, FIG. 3(A) ].
  • the n-GaAs layer 4 A and the n-InGaP layer 7 A are etched to form the n-InGaP diffraction grating 7 having the n-GaAs cap layer 4 B on an upper part thereof.
  • the SiO 2 film 20 is removed, and, as shown in FIG. 3(C) , by the MOCVD method for example, the temperature is raised in an atmosphere of PH 3 which is a P material until 400° C. to prevent P from desorbing from the n-InGaP diffraction grating 7 .
  • PH 3 a P material
  • Ga is supplied in an atmosphere of AsH 3 which is an As material at 400° C. to grow an n-GaAs buried layer 4 C with a small thickness so that the n-GaAs buried layer 4 C covers the n-InGaP diffraction grating 7 having the n-GaAs cap layer 4 B on an upper part thereof.
  • the supplying of Ga is temporarily stopped, the temperature is raised at 600° C. while flowing AsH 3 , and thereafter, Ga is supplied in the AsH 3 atmosphere to grow the n-GaAs buried layer 4 C, whereby the n-GaAs guide layer 4 including the n-InGaP diffraction grating 7 is formed.
  • the n-GaAs guide layer 4 is constituted of the n-GaAs cap layer 4 B and the n-GaAs buried layer 4 C.
  • the n-GaAs buried layer 4 C is grown such that the n-InGaP diffraction grating 7 having the n-GaAs cap layer 4 B on an upper part thereof is buried in the n-GaAs buried layer 4 C to form the n-GaAs guide layer 4 .
  • the degradation of the shape of the n-InGaP diffraction grating 7 (for example, degradation due to the desorption of P) can be prevented.
  • the diffraction grating is formed from InGaP, and an oxide is less likely to be formed on the surface in the etching, whereby the InGaP diffraction grating 7 can be buried with the n-GaAs guide layer 4 , that is, the diffraction grating 7 can be formed in the semiconductor stacked structure.
  • the InGaP diffraction grating 7 is buried with the GaAs guide layer 4 , and the semiconductor material not containing Al is used, whereby an oxide is less likely to be formed on the surface in the etching for the formation of the diffraction grating 7 . Therefore, the high temperature process (high temperature processing) for removing the oxide is not required to be performed, and, at the same time, the processes after the formation of the quantum dot active layer 3 can be performed at a temperature lower than the temperature thermally deteriorating or degrading the quantum dots.
  • the quantum dot semiconductor light emitting device index coupled DFB laser using quantum dot
  • the quantum dot semiconductor light emitting device having the diffraction grating 7 in the semiconductor stacked structure can be manufactured without thermally deteriorating or degrading the quantum dots.
  • the n-AlGaAs upper cladding layer 5 (in this embodiment, n-Al 0.35 Ga 0.65 As upper cladding layer) and the n-GaAs contact layer 6 are sequentially stacked at 600° C. (third growth, see FIG. 1 ).
  • the SiO 2 film is formed, and the ridge waveguide pattern is formed on the SiO 2 film by using a photolithography technique, for example.
  • the SiO 2 film with the ridge waveguide pattern formed there in is used as a mask, and the pattern is transferred to the n-GaAs contact layer 6 , the n-AlGaAs upper cladding layer 5 , and the n-GaAs guide layer 4 including the n-InGaP diffraction grating 7 by chlorine-based dry etching, for example (namely, regarding the n-GaAs contact layer 6 , the n-AlGaAs upper cladding layer 5 , and the n-GaAs guide layer 4 including the n-InGaP diffraction grating 7 , each part which is not covered with the SiO 2 mask is removed) to expose the InAs quantum dot active layer 3 , whereby the ridge structure 8 , which includes the n-GaAs contact layer 6 , the n-AlGaAs upper cladding layer 5 , and the n-GaAs guide layer 4 including the n-G
  • SiO 2 film 17 SiO 2 passivation film 17 (see, FIG. 2 ) so as to cover the ridge structure 8 .
  • electrodes 18 and 19 for electrical current injection are formed in the upper and lower parts of the ridge structure 8 (see, FIG. 2 ).
  • the facet coating is applied after cleavage in array form. For instance, when the device length is 300 ⁇ m, the anti-reflection coating may be applied to the front facet, and the high reflection coating may be applied to the back facet.
  • the diffraction grating 7 can be formed in the semiconductor stacked structure by a manufacturing method (regrowth technique) which, after the semiconductor layer 7 A is grown and the diffraction grating 7 is formed by etching, other semiconductor layer 4 is grown again, and at the same time, there is an advantage that the transverse mode can be easily controlled, whereby a sufficient coupling constant can be obtained. Additionally, there is also an advantage that, in comparison with the loss coupled DFB laser using quantum dot, the threshold current can be lowered.
  • the diffraction grating 7 can be formed in the semiconductor stacked structure while preventing the quantum dots from being thermally deteriorated or degraded (namely, without undergoing the high temperature process).
  • the diffraction grating 7 is formed from the n-type InGaP, it may be formed from, for example, undoped InGaP (i-InGaP) in which n-type impurities are not doped. However, in this case, an electric current is less likely to flow to cause increase of resistance.
  • the diffraction grating may be formed from n-type InGaAsP or undoped InGaAsP (i-InGaAsP) lattice-matched to GaAs.
  • the guide layer 4 (diffraction grating buried layer) including the diffraction grating 7 is formed from n-type GaAs, it may be formed from, for example, undoped GaAs (i-GaAs) in which the n-type impurities are not doped. However, in this case, the device resistance is increased.
  • the ridge bottom face may be formed at an intermediate part of the GaAs guide layer to expose the GaAs guide layer on the opposite sides of the ridge structure.
  • the quantum dot active layer 3 is the p-type quantum dot active layer with the p-type impurities doped in a part thereof, it may be constituted as an undoped quantum dot active layer without the p-type impurities.
  • the upper cladding layer 5 and the lower cladding layer 2 are formed from AlGaAs, it may be formed from InGaP, for example.
  • the resistance and heat-resistance tend to be increased in comparison with the case in which those layers are formed from AlGaAs, there is an effect that the index coupled semiconductor light emitting device using quantum dot (index coupled DFB laser using quantum dot) can be manufactured while suppressing the thermal degradation of the quantum dots, because, as with the case in which the upper cladding layer 5 and the lower cladding layer 2 are formed from AlGaAs, these layers can be grown at a temperature lower than the temperature thermally deteriorating or degrading the quantum dots.
  • the diffraction grating 7 may be constituted to have ⁇ /4 wavelength shift.
  • the composition ratio between the p-AlGaAs cladding layer and the n-AlGaAs cladding layer is not limited to the above.
  • the composition of the upper and lower cladding layers are not required to be the same.
  • each layer is grown by the combination of the MBE method and the MOCVD method, it may be grown by any one growth method of the MBE method, the MOCVD method, a gas source MBE method, and other methods, or these methods may be appropriately combined to grow each layer.
  • the MBE method since cleaning by annealing process (heat treatment) is required before growth, the MBE method is not unsuitable for the regrowth process.
  • the first and second growth in the first embodiment are performed by the same growth method, it is preferable that the first and second growth are continuously performed.
  • the diffraction grating 7 is formed by wet etching, it may be formed by dry etching, for example, and it may be formed by the combination of the dry etching and the wet etching.
  • a resist may be used as an etching mask instead of the SiO 2 film.
  • the selective etching is used for the interface part between the active layer and the diffraction grating.
  • the n-InGaP layer 7 A and the n-GaAs layer 4 A are sequentially stacked on the i-GaAs layer 16 [see, FIG. 3(A) ] and etched to form the diffraction grating 7 , and thereafter, to grow the n-GaAs buried layer 4 C, whereby the n-GaAs guide layer 4 is formed [see, FIG. 3(B) ].
  • an n-GaAs layer, an n-InGaP layer, an n-GaAs layer are sequentially stacked on the quantum dot active layer 3 and etched to form the diffraction grating 7 , and thereafter, to grow the n-GaAs buried layer, whereby n-GaAs guide layer 4 may be formed.
  • the etching for forming the diffraction grating 7 since the n-GaAs layer is formed below the diffraction grating 7 , that is, between the quantum dot active layer 3 and the n-InGaP layer 7 A forming the diffraction grating 7 , in the etching for forming the diffraction grating 7 , the etching only has to be stopped at the intermediate part of the n-GaAs layer formed below the diffraction grating 7 . Therefore, even if the selective etching is not used for the formation of the diffraction grating 7 , the narrow line-shaped diffraction grating 7 can be formed.
  • the n-GaAs guide layer 4 has the n-GaAs layer also below the diffraction grating 7 , that is, between the quantum dot active layer 3 and the diffraction grating 7 .
  • the semiconductor light emitting device according to the second embodiment is different from the first embodiment and the modification in having a current blocking layer.
  • the semiconductor light emitting device is provided with, above a GaAs layer (GaAs guide layer) 4 , an n-type AlAs current blocking layer 21 having a current blocking part 21 A (formed from an AlAs oxide film (Al x O y ) obtained by oxidizing an AlAs layer, in this embodiment) adjacent to the side of the ridge structure (ridge waveguide) 8 .
  • an n-type AlAs current blocking layer 21 having a current blocking part 21 A formed from an AlAs oxide film (Al x O y ) obtained by oxidizing an AlAs layer, in this embodiment
  • FIGS. 5 and 6 components same as those in the first embodiment (see, FIGS. 1 and 2 ) and the modification (see, FIG. 4 ) are represented by same numbers.
  • the semiconductor light emitting device (index coupled semiconductor light emitting device using quantum dot; index coupled DFB laser using quantum dot in the present embodiment) is provided with a p-type GaAs substrate (p-type conductive substrate) 1 , a p-type AlGaAs lower cladding layer 2 formed over the p-type GaAs substrate 1 , a quantum dot active layer 3 formed over the p-type AlGaAs lower cladding layer 2 , an n-type GaAs guide layer 4 formed over the quantum dot active layer 3 and including an n-type InGaP diffraction grating 7 , an n-type AlAs current blocking layer 21 formed over the n-type GaAs guide layer 4 , an n-type AlGaAs upper cladding layer 5 formed over the n-type AlAs current blocking layer 21 , and an n-type GaAs contact layer 6 formed over the n-type AlGaAs upper
  • the quantum dot semiconductor light emitting device in this embodiment has a stacked structure in which the p-type AlGaAs lower cladding layer 2 , the quantum dot active layer 3 , the n-type GaAs guide layer 4 including an n-type InGaP diffraction grating 7 , the n-type AlAs current blocking layer 21 , the n-type AlGaAs upper cladding layer 5 , and the n-type GaAs contact layer 6 are sequentially stacked over the p-type GaAs substrate 1 .
  • the p-type AlGaAs lower cladding layer 2 , the quantum dot active layer 3 , and the n-GaAs guide layer 4 including the narrow line-shaped n-InGaP diffraction grating 7 are formed on the p-type GaAs substrate 1 [see, FIG. 3(A) ].
  • the n-AlAs current blocking layer 21 , the n-AlGaAs upper cladding layer 5 , and the n-GaAs contact layer 6 are sequentially stacked at 600° C. (third growth; see, FIG. 5 ).
  • the SiO 2 film is formed, and the ridge waveguide pattern is formed on the SiO 2 film by using a photolithography technique, for example.
  • the SiO 2 film with the ridge waveguide pattern formed therein is used as a mask, and the pattern is transferred to the n-GaAs contact layer 6 , the n-AlGaAs upper cladding layer 5 , the n-AlAs current blocking layer 21 , and the n-GaAs guide layer 4 including the n-InGaP diffraction grating 7 by chlorine-based dry etching, for example (namely, regarding the n-GaAs contact layer 6 , the n-AlGaAs upper cladding layer 5 , the n-AlAs current blocking layer 21 , and the n-GaAs guide layer 4 including the n-InGaP diffraction grating 7 , each part which is not covered with the SiO 2 mask is removed) to expose the InAs quantum dot active layer 3 , whereby the ridge structure 8 , which includes the n-GaAs contact layer 6 , the n-Al
  • the n-AlAs current blocking layer 21 is oxidized under a water vapor atmosphere to form a current blocking part 21 A, which is formed from AlAs oxide film (Al x O y ), adjacent to the side of the ridge waveguide 8 (see, FIG. 6 ).
  • SiO 2 mask is removed, and an SiO 2 passivation film (SiO 2 film) 17 is formed so as to cover the ridge structure 8 (see, FIG. 6 ).
  • electrodes 18 and 19 for electrical current injection are formed at the top and the bottom (see, FIG. 6 ).
  • the facet coating is applied after cleavage in array form. For instance, when the device length is 300 ⁇ m, the anti-reflective coating may be applied to the front facet and the high reflective coating may be applied to the back facet.
  • the semiconductor light emitting device and the method for manufacturing the semiconductor light emitting device according to this embodiment in addition to the effects of the first embodiment and the modification, since a current blocking structure using the AlAs oxide film (Al x O y ) is formed, there is an advantage that the semiconductor light emitting device (index coupled DFB laser), in which a threshold current is lowered without reducing the contact resistance, can be realized.
  • the n-AlAs current blocking layer 21 is provided above the GaAs guide layer (GaAs layer) 4 , it is not limited thereto.
  • an n-AlAs current blocking layer may be provided below the GaAs layer 4 (namely, between the GaAs layer 4 and the quantum dot active layer 3 ) (in this case, the AlAs current blocking layer forms the ridge bottom face).
  • the diffraction grating is separated from the active layer, whereby the coupling constant tends to be reduced.
  • the n-AlGaAs current blocking layer may be provided above the GaAs layer 4 , or may be provided below the GaAs layer 4 (namely, between the GaAs layer 4 and the quantum dot active layer 3 ).
  • the composition of Ga in the n-AlGaAs current blocking layer is large, the speed of formation of the current blocking part by oxidation is reduced.
  • the presence or absence of doping in the InGaP diffraction grating and the guide layer, the growth method and the frequency of growth, the depth of the ridge, the method for ridge formation, the method for diffraction grating formation, a diffraction grating material, the number of stacked layers in the quantum dot active layer, the AlGaAs composition ratio in the cladding layer, a cladding layer material, the presence or absence of the ⁇ /4 wavelength shift structure in the diffraction grating, and so on can be changed into various forms.
  • the semiconductor light emitting device according to this embodiment is different from the semiconductor light emitting device according to the first embodiment and the modification in that it is formed on an n-type GaAs substrate (n-type conductive substrate) 1 X and a GaAs guide layer (GaAs layer) 4 is provided below a quantum dot active layer 3 X, that is, provided between the quantum dot active layer 3 X and a lower cladding layer 2 X.
  • a GaAs guide layer GaAs layer 4
  • FIGS. 7 and 8 the components same as those in the first embodiment (see, FIGS. 1 and 2 ) and the modification (see, FIG. 4 ) are represented by same numbers.
  • the semiconductor light emitting device (index coupled semiconductor light emitting device using quantum dot; index coupled DFB laser using quantum dot in the present embodiment) is provided with the n-type GaAs substrate (n-type conductive substrate) 1 X, an n-type AlGaAs lower cladding layer 2 X (in this embodiment, n-Al 0.35 Ga 0.65 As lower cladding layer) formed over the n-type GaAs substrate 1 X, the n-type GaAs guide layer 4 , which is formed over the n-type AlGaAs lower cladding layer 2 X and includes an n-type InGaP diffraction grating 7 , the quantum dot active layer 3 X formed over the n-type GaAs guide layer 4 , a p-type AlGaAs upper cladding layer 5 X (in this embodiment, p-Al 0.35 Ga 0.65 As upper cladding layer) formed over the quantum dot active layer
  • the quantum dot semiconductor light emitting device in this embodiment has a stacked structure in which the n-type AlGaAs lower cladding layer 2 X, the n-type GaAs guide layer 4 including the n-type InGaP diffraction grating 7 , the quantum dot active layer 3 X, the p-type AlGaAs upper cladding layer 5 X, and the p-type GaAs contact layer 6 X are sequentially stacked on the n-type GaAs substrate 1 X.
  • the diffraction grating 7 is formed from InGaP, an oxide is difficult to be formed on a surface in the etching, and the diffraction grating 7 can be buried with the GaAs layer 4 , whereby the diffraction grating 7 can be formed in the semiconductor stacked structure.
  • the GaAs guide layer 4 is required to be formed to have a large thickness for the purpose of burying the diffraction grating 7 completely flatly. Thus, it is necessary to pay attention to that the coupling constant tends to be reduced.
  • the quantum dot active layer 3 X is the undoped InAs quantum dot active layer (i-InAs quantum dot active layer) 3 X in which the p-type impurities are not doped, and has a stacked structure in which a layer (quantum dot layer) composed of InAs quantum dots 10 , an i-InAs wetting layer 11 , an i-InGaAs strain relaxation layer (side barrier layer) 12 formed to cover the InAs quantum dots 10 , and an i-GaAs layer (barrier layer) 13 X are repeatedly stacked a plurality of times (10 times in this embodiment) on an i-GaAs layer (barrier layer) 9 .
  • the number of the stacked layers in the quantum dot active layer 3 X is not limited to the above, and can be changed depending on the intended use of the semiconductor light emitting device, for example.
  • the quantum dot semiconductor light emitting device in this embodiment is constituted as a ridge waveguide type quantum dot semiconductor light emitting device (ridge waveguide type quantum dot DFB laser) having a ridge structure (stripe structure; stripe-shaped mesa structure) 8 including a p-type GaAs contact layer 6 ⁇ and the p-type AlGaAs upper cladding layer 5 X.
  • ridge waveguide type quantum dot DFB laser ridge waveguide type quantum dot DFB laser
  • the upper surface of the quantum dot active layer 3 X is exposed over the opposite sides (both sides) of the ridge structure 8 . Namely, the quantum dot active layer 3 X extends to the end face of the n-type GaAs substrate 1 X.
  • the first growth may use the MOCVD method.
  • the semiconductor light emitting device and the method for manufacturing the semiconductor light emitting device according to this embodiment have the same effect as the first embodiment and the modification.
  • the undoped InAs quantum dot active layer 3 X is used, as with the first and second embodiments and these modifications, the p-type quantum dot active layer may be used for example.
  • the p-n junction are a becomes large, it is necessary to pay attention to that the capacitance of the device is increased, whereby it is unsuitable for a high speed modulation operation.
  • the p-type AlAs current blocking layer (or p-type AlGaAs current blocking layer) 21 X having a current blocking part 21 AX may be provided adjacent to the side of the ridge structure (ridge waveguide) 8 so as to be sandwiched with the p-type AlGaAs upper cladding layer 5 ⁇ [see, FIG. 9(A) ], or may be provided between the quantum dot active layer 3 ⁇ and the p-type AlGaAs upper cladding layer 5 ⁇ [see, FIG. 9(B) ].
  • the composition ratio between the p-AlGaAs cladding layer and the n-AlGaAs cladding layer is not limited to the above ratio.
  • the composition of the upper and lower cladding layers are not required to be the same.
  • the presence or absence of doping in the InGaP diffraction grating and the guide layer, the growth method and the frequency of growth, the depth of the ridge, the method for ridge formation, the method for diffraction grating formation, a diffraction grating material, the number of stacked layers in the quantum dot active layer, the AlGaAs composition ratio in the cladding layer, a cladding layer material, the presence or absence of the ⁇ /4 wavelength shift structure in the diffraction grating, and so on can be changed into various forms.
  • the semiconductor light emitting device in which the quantum dot active layers 3 and 3 X formed from the InAs-based compound semiconductor material are respectively formed on the GaAs substrates 1 and 1 X, is described, it is not limited thereto.
  • the semiconductor light emitting device can be constituted to have a quantum dot active layer formed from other semiconductor material (for example, a quantum dot active layer formed from a semiconductor material based on other material capable of constituting a semiconductor laser).
  • a quantum dot active layer formed from an InAsSb-based compound semiconductor material which can be produced on the GaAs substrate
  • a quantum dot active layer formed from InNAs-based compound semiconductor material which can be produced on the GaAs substrate
  • a quantum dot active layer formed from an InNAsSb-based compound semiconductor material formed from an InNAsSb-based compound semiconductor material.
  • the semiconductor light emitting device is constituted to be formed on the n-type conductive substrate 1 X or the p-type conductive substrate 1 , it may be formed on a high resistance substrate, for example.
  • the semiconductor light emitting device can be constituted as a lateral current injection type semiconductor light emitting device (a lateral current injection type semiconductor laser) formed on the high resistance substrate.
  • the lateral current injection type semiconductor light emitting device has a stacked structure in which a p-AlGaAs lower cladding layer 2 , a p-GaAs contact layer 22 , a quantum dot active layer 3 , an n-GaAs guide layer (n-GaAs layer) 4 including an n-InGaP diffraction grating 7 , an n-AlGaAs upper cladding layer 5 , and an n-GaAs contact layer 6 are sequentially stacked on a high-resistance GaAs substrate 1 Y, and has a ridge structure 8 including the n-GaAs guide layer 4 , the n-AlGaAs upper cladding layer 5 , and then GaAs contact layer 6 .
  • the lateral current injection type semiconductor light emitting device has on its surface an insulating film (SiO 2 film) 17 formed from SiO 2 , an n-side electrode 18
  • a high resistance GaAs substrate 1 Y is used, the high-resistance GaAs substrate 1 Y and the p-AlGaAs lower cladding layer 2 are extended, the p-GaAs contact layer 22 is provided between the p-AlGaAs lower cladding layer 2 and the quantum dot active layer 3 , and the p-side electrode 19 is provided on the p-GaAs contact layer 22 .
  • this embodiment is described as the modification of the first embodiment, it can be constituted as a modification of the second and third embodiments, for example.
  • the semiconductor light emitting device is constituted as a distributed feed-back laser (DFB laser) having a diffraction grating
  • DBR laser distributed bragg reflector laser
  • the semiconductor laser of a 1.3 ⁇ m wavelength band is described as an example, the invention can be widely applied to a semiconductor laser (semiconductor light emitting device) with a wavelength band of the operation wavelength longer than 1 ⁇ m, such as a semiconductor layer of a 1.2 ⁇ m wavelength band used in a short range LAN, for example, and a semiconductor laser of a 1.06 ⁇ m wavelength band used for YAG laser excitation.
  • a semiconductor laser semiconductor light emitting device with a wavelength band of the operation wavelength longer than 1 ⁇ m, such as a semiconductor layer of a 1.2 ⁇ m wavelength band used in a short range LAN, for example, and a semiconductor laser of a 1.06 ⁇ m wavelength band used for YAG laser excitation.
  • the ridge waveguide type semiconductor light emitting device is described as an example, the invention can be applied to a buried-type semiconductor light emitting device which has a stripe-shaped mesa structure (stripe structure) and a buried-heterostructure such as a pn buried structure and a high resistance buried structure.

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