CN111755947B - Asymmetric structure high-power laser with Bragg reflector and preparation method thereof - Google Patents

Asymmetric structure high-power laser with Bragg reflector and preparation method thereof Download PDF

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CN111755947B
CN111755947B CN201910250940.9A CN201910250940A CN111755947B CN 111755947 B CN111755947 B CN 111755947B CN 201910250940 A CN201910250940 A CN 201910250940A CN 111755947 B CN111755947 B CN 111755947B
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CN111755947A (en
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刘飞
邓桃
王朝旺
郑兆河
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Weifang Huaguang Photoelectronics Co ltd
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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
    • H01S5/343—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
    • H01S5/34346—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 characterised by the materials of the barrier layers
    • H01S5/34353—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 characterised by the materials of the barrier layers based on (AI)GaAs
    • 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
    • H01S5/10—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
    • H01S5/18—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities
    • H01S5/185—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities having only horizontal cavities, e.g. horizontal cavity surface-emitting lasers [HCSEL]
    • H01S5/187—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities having only horizontal cavities, e.g. horizontal cavity surface-emitting lasers [HCSEL] using Bragg reflection
    • 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
    • H01S5/34346—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 characterised by the materials of the barrier layers
    • H01S5/3436—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 characterised by the materials of the barrier layers based on InGa(Al)P
    • 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
    • H01S5/34346—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 characterised by the materials of the barrier layers
    • H01S5/3438—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 characterised by the materials of the barrier layers based on In(Al)P

Abstract

The invention relates to an asymmetric structure with a Bragg reflectorA power laser and a preparation method thereof belong to the field of lasers, and comprise a GaAs substrate, wherein the GaAs substrate comprises a GaAs buffer layer and Ga which are sequentially deposited from bottom to top1‑xInxP transition layer, Al1‑ xInxP lower limiting layer, (Al)1‑xGax)yIn1‑yP lower waveguide layer, Ga1‑ xInxP quantum well luminous zone, (Al)1‑xGax)yIn1‑yP upper waveguide layer, Al1‑xGaxAs Bragg reflective layer and Al1‑xGaxAn As upper confinement layer and a GaAs cap layer. The invention can obtain narrower spectral line width, effectively reduce internal loss, reduce heat generation, improve electro-optic conversion efficiency, and improve the stability and service life of the device, thereby realizing wider application of 630-plus-710 nm series high-power semiconductor lasers in long distance, multi-path and the like.

Description

Asymmetric structure high-power laser with Bragg reflector and preparation method thereof
Technical Field
The invention relates to an asymmetric structure high-power laser with a Bragg reflector and a preparation method thereof, belonging to the technical field of lasers.
Background
The semiconductor laser has the advantages of small volume, light weight, high reliability, high electro-optic conversion efficiency, good beam quality and the like, and is widely applied to various fields such as military, medical treatment, industry and the like. While the applications in military, medical and industrial fields mostly require that the semiconductor laser has high power output, but the high-power semiconductor laser has a high internal loss mechanism, so the electro-optical conversion efficiency is still very low, and a large amount of heat is generated in the using process, so that the stability and the service life of the device are influenced.
The control of heat generation plays an important role in the reliability of the laser, and the main source of the heat is the internal loss of the semiconductor laser, so that the internal loss is reduced to reduce the generation of heat, thereby improving the reliability and the service life of the semiconductor laser.
The loss of the laser mainly comes from the following aspects: (1) spontaneous emission below a threshold; (2) voltage loss due to the heterojunction band structure; (3) active region carrier leakage loss; (4) laser cavity and absorption and scattering of photons, etc. Theoretically, the loss can be reduced by five methods, namely, improving the internal differential quantum of the device, reducing the built-in voltage of the carrier injected into the quantum well, reducing the series resistance and the threshold current, reducing the limiting factors of the quantum well and the cladding and reducing the carrier absorption coefficient. To reduce the internal loss of the laser, a great deal of research is carried out: (i) the structural parameters of the limiting layer are adjusted, the effective refractive index of the semiconductor device is changed, the better limiting effect of the limiting layer on the optical field is realized, and the leakage of current carriers is reduced; (ii) ohmic contact resistance is reduced by improving the doping concentration of a metal and semiconductor interface, and the series resistance of the whole device can be reduced by optimizing the doping concentration of the waveguide and the cladding; (iii) increasing optical confinement and optimizing the overlap of the optical field and the quantum well, reducing scattering loss, selecting correct doping distribution, improving the quality of semiconductor crystals, and reducing the absorption loss of free carriers; (IV) voltage loss caused by the heterojunction energy band structure can be realized by the gradual change of the components of the heterojunction interface and the change of doping; (V) reducing losses with an asymmetric waveguide structure. The approach of using an asymmetric waveguide structure is due to the fact that the absorption of photons by holes in the p-type material region is greater than the absorption of photons by electrons in the n-type material region. The asymmetric waveguide structure is adopted to change the refractive index distribution of the epitaxial structure, so that the optical field is far away from the p-type side of the device and enters the n-type material, and the absorption of free carriers to photons can be reduced.
However, most of the current research on reducing the loss in the laser is focused on 8XX and 9XX series semiconductor lasers with the wavelength of 800nm to 980nm, and less research is conducted on 630nm to 710nm series (6XX series) semiconductor lasers.
The red visible semiconductor laser with the light-emitting wavelength within the range of 630nm-710nm has extremely high application potential in the fields of medical treatment, data storage, pumping, laser display and the like, and the epitaxial structure generally comprises a GaInP quantum well, an AlGaInP waveguide layer, an Al (Ga) InP limiting layer, a GaAs cap layer and the like. However, (1) this structure is prone to leakage of electron and hole carriers due to the reduced barrier height, resulting in reduced internal quantum efficiency and greater sensitivity to operating temperatures; (2) the limiting layer needs higher carrier concentration to reduce the series resistance, the commonly used P limiting layer dopant, Zn has lower doping concentration and large diffusion coefficient in Al (Ga) InP, Mg is more sensitive to O element and has strong memory effect at the same time, which is not beneficial to improving the high temperature reliability; (3) the absorption capacity of the holes in the p-type material region to photons is larger than that of the electrons in the n-type material region to photons, and the absorption of the holes to the photons can be reduced only to a certain extent by the asymmetric waveguide structure, so that a more effective means for improving the internal quantum efficiency is needed urgently.
The invention content is as follows:
aiming at the defects of the conventional 630-series 710nm semiconductor laser, the invention provides the asymmetric-structure high-power laser with the Bragg reflector and the preparation method thereof, which can obtain narrower spectral line width and higher power, effectively reduce internal loss, reduce heat generation, improve electro-optic conversion efficiency, and improve the stability and the service life of the device, thereby realizing the wider application of the 630-series 710nm high-power semiconductor laser in long distance, multiple paths and the like.
The invention adopts the following technical scheme:
an asymmetric structure high-power laser with a Bragg reflector comprises a GaAs substrate, wherein the GaAs substrate comprises a GaAs buffer layer and Ga which are deposited from bottom to top in sequence1-xInxP transition layer, Al1-xInxP lower limiting layer, (Al)1-xGax)yIn1-yP lower waveguide layer, Ga1-xInxP quantum well luminous zone, (Al)1-xGax)yIn1-yP upper waveguide layer, Al1-xGaxAs Bragg reflective layer (DBR), Al1-xGaxAn As upper confinement layer and a GaAs cap layer.
A bragg reflector (DBR) is a mirror structure comprising an adjustable multilayer structure of two optical materials, most commonly a quarter-mirror, wherein each layer has a thickness corresponding to a quarter wavelength, so that the stimulated emission light has the same frequency, phase, polarization and propagation direction as the extraneous stimulated emission-causing light. Through the stimulated radiation, homomorphic photon number amplification can be realized, and coherent light with extremely high photon degeneracy is obtained.
Preferably, the (Al) is1-xGax)yIn1-yThickness of P lower waveguide layer and (Al)1-xGax)yIn1-yThe upper waveguide layers have different thicknesses, and the lower waveguide layer has a thickness greater than that of the upper waveguide layer. The structure can reduce threshold current and series resistance, reduce internal loss, and realize stability and service life of the 6XX series laser during high-power work.
A preparation method of the asymmetric structure high-power laser with the Bragg reflector comprises the following steps:
(1) placing the GaAs substrate in MOCVD equipment, H2The environment is heated to 720 +/-10 ℃ and baked for 30 minutes, and AsH is introduced3Removing water and oxygen on the surface of the GaAs substrate to finish surface heat treatment and preparing for the step (2);
(2) slowly reducing the temperature to 700 +/-10 ℃, and continuously introducing TMGa and AsH3Growing a GaAs buffer layer with the thickness of 0.3-1 mu m on the GaAs substrate;
(3) keeping the temperature at 700 +/-10 ℃, and continuously introducing TMIn, TMGa and PH3Growing Ga on the GaAs buffer layer of the step (2)1-xInxA P transition layer;
(4) keeping the temperature at 700 +/-10 ℃, and continuously introducing TMIn, TMAl and PH3Ga in step (3)1-xInxGrowing n-type Al on the P transition layer1-xInxA P lower limiting layer;
(5) the temperature is reduced to 650 +/-10 ℃, and TMIn, TMAl, TMGa and PH are continuously introduced3Al in step (4)1-xInxGrowth on P lower confinement layer (Al)1-xGax)yIn1-yA P lower waveguide layer;
(6) keeping the temperature at 650 +/-10 ℃, and continuously introducing TMIn, TMGa and PH3At step (5) (Al)1-xGax)yIn1-yGa growing on P lower waveguide layer1-xInxA P quantum well light emitting region;
(7) raising the temperature to 700 +/-10 ℃, and continuously introducing TMIn, TMAl, TMGa and PH3Ga in step (6)1-xInxGrowth on P quantum well light-emitting region (Al)1-xGax)yIn1-yA P upper waveguide layer;
(8) keeping the temperature at 700 +/-10 ℃, and continuously introducing TMAl, TMGa and AsH3(Al) at step (7)1-xGax)yIn1-yGrowing P-type Al on the P upper waveguide layer1-xGaxAs/Al1-xGaxThe number of the circulating logarithm of the As Bragg reflecting layer is z, and z is more than 0 and less than or equal to 100;
(9) keeping the temperature at 700 +/-10 ℃, and continuously introducing TMGa, TMAl and AsH in the step (8)3Growing Al on the Bragg reflection layer of the step (8)1-xGaxAn As upper confinement layer;
(10) reducing the temperature to 550 +/-10 ℃, closing TMAl, and continuously introducing TMGa and AsH3Al in step (9)1- xGaxGrowing a GaAs cap layer on the As upper limiting layer;
(11) and after the growth is finished, manufacturing a finished laser by adopting a packaging technology. After the epitaxial layer is grown by using the MOCVD technology, the epitaxial wafer needs to be manufactured by a tube core process and a packaging process subsequently, and finally a device of the semiconductor laser is formed.
Preferably, the pressure of the MOCVD equipment during the preparation process is 50-200 mbar.
Preferably, the GaAs buffer layer and the Al layer are formed of a single layer or a single layer1-xInxThe N-type doping sources of the P lower limiting layer are all Si2H6(ii) a The Al is1- xGaxAs/Al1-xGaxAs Bragg reflective layer and Al1-xGaxThe doping sources of the A upper limiting layer and the GaAs cap layer are both CBr4。
Preferably, H2The flow rate of the flow is 8000-50000 sccm; the purity of the TMGa is 99.9999%, and the temperature of a constant temperature bath of the TMGa is (-5) to 15 ℃; the purity of the TMIn is 99.9999 percent, soThe temperature of the constant temperature tank of the TMIn is 10-25 ℃; the purity of the TMAl is 99.9999%, and the temperature of a constant temperature tank of the TMAl is 10-25 ℃; the AsH3The purity of (2) is 99.9999%; said Si2H6The purity of (2) is 99.9999%; the CBr4The temperature of the constant temperature bath is 10-25 ℃.
Preferably, in the step (2), the thickness of the GaAs buffer layer is 300-500nm, and the doping concentration is 1E17-5E18 atoms/cm3
Preferably, the thickness of the GaAs buffer layer in the step (2) is 300nm, and the doping concentration is 1E18 atoms/cm3；
Preferably, Ga is used in step (3)1-xInxThe doping concentration of the P transition layer is 1E17-5E18 atoms/cm3，0.45≤x≤0.55；
Preferably, Ga is used in step (3)1-xInxThe doping concentration of the P transition layer is 1E18 atoms/cm3The thickness was 0.2. mu.m, and x was 0.52.
Preferably, in the step (4), n-type Al1-xInxThe thickness of the P lower limiting layer is 0.5-2 μm, and the doping concentration is 1E17-5E18 atoms/cm3；
Preferably, n-type Al1-xInxThe thickness of the P lower limiting layer is 1 μm, and the doping concentration is 1E18 atoms/cm3；
Preferably, 0.3. ltoreq. x.ltoreq.0.6.
Preferably, step (5) (Al)1-xGax)yIn1-yX is more than or equal to 0.4 and less than or equal to 0.6, y is more than or equal to 0.4 and less than or equal to 0.6 in the P lower waveguide layer, the thickness is 0.1-0.2 mu m, the P lower waveguide layer is not intentionally doped, and the intrinsic doping concentration is 1E16-5E16 atoms/cm3；
Preferably, step (5) (Al)1-xGax)yIn1-yThe thickness of the P lower waveguide layer is 0.12 μm, and the intrinsic doping concentration is 1E16 atoms/cm3。
Preferably, Ga in step (6)1-xInxThe thickness of the P quantum well light-emitting region is 5-15nm, the P quantum well light-emitting region is not intentionally doped, and x is more than 0.45 and less than 0.55;
(Al) in step (7)1-xGax)yIn1-yThe thickness of the P upper waveguide layer is 0.05-0.15 μm, and the P upper waveguide layer is unintentionally doped with intrinsic doping concentration of 1E16-5E16 atoms/cm3；
Preferably, step (7) (Al)1-xGax)yIn1-yThe thickness of the P upper waveguide layer is 0.07 μm, and the intrinsic doping concentration is 1E16 atoms/cm3，0.4≤x≤0.6，0.4≤y≤0.6。
Preferably, in step (8), z is 5 to 30, Al1-xGaxAs/Al1-xGaxX in the As Bragg reflecting layer is more than or equal to 0 and less than or equal to 0.55;
the thickness of the Bragg reflection layer in the step (8) is 0.1-0.5 mu m, and the doping concentration is 1E18-5E18 atoms/cm3；
Preferably, the thickness of the bragg reflector layer in the step 8 is 0.2 μm, and the doping concentration is 3E18 atoms/cm3。
Preferably, in the step (9), x is 0.1. ltoreq. x.ltoreq.0.3, and the doping concentration of the AlGaAs upper cladding layer is 5E18 to 5E19 atoms/cm3；
Preferably, x of the step (9) is 0.15, the thickness is 1 μm, and the doping concentration is 1E19 atoms/cm3。
The invention adopts PECVD method to grow SiO on the AlGaAs upper limiting layer2Insulating film, SiO2The insulating film has the advantages of good compactness, good adhesion, low conductivity and the like, can be deposited in a large area, is suitable for industrial production, and is SiO2The thickness of the insulating film is between 100-200 nm. And after the silicon dioxide insulating layer is deposited, photoetching and etching are carried out, and a current injection window is prepared.
Preferably, in order to obtain good ohmic contact and make the chip beneficial to current injection and heat dissipation, metal films need to be prepared on the p surface and the n surface of the semiconductor laser chip, and a single-layer metal film or a multi-layer metal film can be prepared by adopting an electron beam evaporation method, and specifically, the material of the metal film and the thickness of the material can be selected according to different semiconductor materials and different doping concentrations. In order to reduce the series resistance of the chip and facilitate current injection, the GaAs cap layer of the semiconductor laser chip is doped by adoptingHigh doping, high concentration up to 5 × 1019cm-3The above. The p surface is sequentially evaporated with Ti/Pt/Au metal film, the outermost layer of the n surface is an n-GaAs substrate with the doping concentration of about 1018cm-3The method of high-temperature annealing can be used to further reduce the series resistance, and is called an alloying step. And the GaAs substrate on the n surface of the chip is sequentially evaporated with the Au/Ge/Ni metal film, and Ge atoms can enter the GaAs substrate layer to form high doping in the whole high-temperature alloying process.
In order to improve the performance of the semiconductor laser, a high-reflection film (HR) and an antireflection film (AR) need to be plated on two cavity surfaces, the performance of the semiconductor laser is seriously influenced by the material performance of the high-reflection film (HR) and the antireflection film (AR), the high-quality cavity surface film can effectively reduce the threshold current of the laser, improve the quantum efficiency and the cavity surface optical catastrophic power density (COD), and meanwhile, the peak wavelength of the laser can be adjusted in a small range through the change of the reflectivity of the AR film and the HR film. The plated dielectric optical film can play a role in processing cavity surface dangling bonds, reducing cavity surface states and the like, and can protect the cavity surface and prevent oxidation and the like in physical forms. High-reflection cavity surface film of high-power semiconductor laser usually adopts Si/SiO2Film system, the light-emitting surface is generally made of SiO2A monolayer film or a bilayer film. Examples of the plating method include an electron beam method, a sputtering method, and ECR chemical vapor deposition.
Because the laser has different electro-optic conversion efficiency, a large part of electric energy is converted into heat energy, and in order to reduce adverse effects on the performance of the laser caused by high temperature caused by waste heat, a reliable method is needed to be adopted to dissipate the heat, and a heat sink is commonly used as a main component for dissipating the heat of the laser in the world. In order to achieve good heat dissipation, the selected heat sink material must have good heat conduction performance, and at the same time, a material which can not have too large difference with the thermal expansion coefficient of the laser product is adopted, so that on one hand, the heat sink material is a good thermal conductor, does not pollute the environment, is matched with the physical property of the laser tube core, and mainly has the same or close thermal expansion coefficient; on the other hand, the laser diode also has the characteristics of easy processing, easy welding with a laser tube core, high reliability and the like. The heat sink material used In the invention is oxygen-free copper, and a layer of In with the thickness of 3 mu m is plated on the surface of the heat sink material by adopting a thermal evaporation mode before use. Because In is softer, the In can automatically release the stress between the tube core and the heat sink, and the tube core fracture caused by different thermal expansion coefficients of the tube core and the heat dust can not occur. When the invention is packaged, the tube core P is arranged on the indium-plated copper heat sink In a downward mode, so that the distance between a hot active layer and hot dust is closer, the heat dissipation performance is improved, and the degradation caused by different thermal expansion coefficients between the heat sink and the tube core is reduced by adopting soft In. And heating the heat sink under the protection of nitrogen during sintering to slowly melt the indium on the heat sink, aligning the front cavity surface of the laser chip with the end surface of the heat sink during crystal solidification, applying a certain pressure on the laser chip to ensure that the indium is fully contacted with the laser tube core, reducing holes between the laser tube core and hot dust, and paying attention to the fact that the indium cannot be adhered to or pollute the cavity surface of the tube core to cause the performance reduction of the laser.
The invention has the beneficial effects that:
1) the invention uses conventional P-type Al1-xInxP confinement layer changed to Al1-xGaxAs limiting layer, and Al is added at the growth interface of upper waveguide layer and upper limiting layer1-xGaxAs/Al1-xGaxThe As Bragg reflection layer enables Fresnel reflection to occur at the interface, the optical path difference of reflected light at two adjacent interfaces is half wavelength when the working wavelength is long, and in addition, the sign of the reflection coefficient at the interface can also be changed. Therefore, all reflected light at the interface undergoes destructive interference, strong reflection is obtained to improve a wider tuning range and a narrower line width, and two independent gratings are integrated in one laser to realize a wider wavelength tuning range, a narrower spectral line width and higher power.
2) The invention adds Al between the upper limiting layer and the waveguide layer1-xGaxAs/Al1-xGaxThe As Bragg reflecting layer enables the light of the stimulated radiation to have the same frequency, phase, polarization and propagation direction with the external light which causes the stimulated radiation. Through stimulated radiation, homomorphic photon number amplification can be realized to obtain coherent light with extremely high photon degeneracy, and simultaneously, the joint use of the DBR, the asymmetric limiting layer and the asymmetric waveguide layer improves 6XX series Al (Ga) InP laserHigh power stability, reliability and life.
3) The structure of the invention adopts asymmetric waveguide layers with different thicknesses, optimizes the optical field to be far away from one side of a P type, and simultaneously adopts a Bragg reflection layer (DBR) to reflect and reduce the absorption loss of upper limiting layer cavity to light; an asymmetric limiting layer is adopted, AlGaAs is used as an upper limiting layer, C is used for replacing Zn and Mg to be used as doping agents, the effective carrier concentration on one side of the upper limiting layer is improved, and the series resistance of a device is reduced; meanwhile, C with a lower thermal diffusion coefficient during high-temperature growth is used as an upper limiting layer dopant, the diffusion distance of C is small, the threshold current is favorably reduced, the diffusion of the dopant to a quantum well is reduced, the internal loss is reduced, the threshold current is reduced, and the reliability and the stability of the 6XX series Al (Ga) InP laser during high-power work are improved.
4) The invention can effectively reduce the internal loss, reduce the generation of heat, improve the electro-optic conversion efficiency, and improve the stability and the service life of the device, thereby realizing the wider application of the 630nm-710nm series high-power semiconductor laser in long distance, multiple paths and the like.
Description of the drawings:
fig. 1 is a schematic structural diagram of an asymmetric-structure high-power laser with a bragg reflector according to the present invention.
The specific implementation mode is as follows:
in order to make the technical problems, technical solutions and advantages of the present invention more apparent, the following detailed description is given with reference to the accompanying drawings and specific examples, but not limited thereto, and the present invention is not described in detail and is in accordance with the conventional techniques in the art.
Example 1:
an asymmetric high-power laser with a Bragg reflector is shown in figure 1 and comprises a GaAs substrate, wherein the GaAs substrate comprises a GaAs buffer layer and Ga which are sequentially deposited from bottom to top1-xInxP transition layer, Al1-xInxP lower limiting layer, (Al)1-xGax)yIn1-yP lower waveguide layer, Ga1-xInxP quantum well luminous zone, (Al)1-xGax)yIn1-yP upper waveguide layer, Al1-xGaxAs Bragg reflective layer and Al1-xGaxAn As upper confinement layer and a GaAs cap layer.
Example 2:
an asymmetric structure high-power laser with a Bragg reflector is disclosed in embodiment 1, except that (Al)1-xGax)yIn1-yThickness of P lower waveguide layer and (Al)1-xGax)yIn1-yThe P upper waveguide layer has different thicknesses, preferably 0.12 μm and 0.07 μm, respectively.
Example 3:
a preparation method of an asymmetric structure high-power laser with a Bragg reflector comprises the following steps:
(1) placing the GaAs substrate in MOCVD equipment, H2The environment is heated to 720 +/-10 ℃ and baked for 30 minutes, and AsH is introduced3Removing water and oxygen on the surface of the GaAs substrate to finish surface heat treatment and preparing for the step (2);
(2) slowly reducing the temperature to 700 +/-10 ℃, and continuously introducing TMGa and AsH3Growing a GaAs buffer layer with the thickness of 0.3 mu m on the GaAs substrate;
(3) keeping the temperature at 700 +/-10 ℃, and continuously introducing TMIn, TMGa and PH3Growing Ga on the GaAs buffer layer of the step (2)1-xInxA P transition layer;
(4) keeping the temperature at 700 +/-10 ℃, and continuously introducing TMIn, TMAl and PH3Ga in step (3)1-xInxGrowing n-type Al on the P transition layer1-xInxA P lower limiting layer;
(5) the temperature is reduced to 650 +/-10 ℃, and TMIn, TMAl, TMGa and PH are continuously introduced3Al in step (4)1-xInxGrowth on P lower confinement layer (Al)1-xGax)yIn1-yA P lower waveguide layer;
(6) keeping the temperature at 650 +/-10 ℃, and continuously introducing TMIn, TMGa and PH3At step (5) (Al)1-xGax)yIn1-yGa growing on P lower waveguide layer1-xInxA P quantum well light emitting region;
(7) raising the temperature to 700 +/-10 ℃, and continuously introducing TMIn, TMAl, TMGa and PH3Ga in step (6)1-xInxGrowth on P quantum well light-emitting region (Al)1-xGax)yIn1-yA P upper waveguide layer;
(8) keeping the temperature at 700 +/-10 ℃, and continuously introducing TMAl, TMGa and AsH3(Al) at step (7)1-xGax)yIn1-yGrowing P-type Al on the P upper waveguide layer1-xGaxAs/Al1-xGaxAn As Bragg reflector layer with a cycle logarithm of z, z being 20;
(9) keeping the temperature at 700 +/-10 ℃, and continuously introducing TMGa, TMAl and AsH in the step (8)3Growing Al on the Bragg reflection layer of the step (8)1-xGaxAn As upper confinement layer;
(10) reducing the temperature to 550 +/-10 ℃, closing TMAl, and continuously introducing TMGa and AsH3Al in step (9)1- xGaxGrowing a GaAs cap layer on the As upper limiting layer;
(11) and after the growth is finished, manufacturing a finished laser by adopting a packaging technology.
Example 4:
a method for preparing a high-power laser with an asymmetric structure and a bragg reflector, as shown in embodiment 3, except that the pressure of an MOCVD device is 100 mbar;
GaAs buffer layer and Al1-xInxThe N-type doping sources of the P lower limiting layer are all Si2H6；Al1-xGaxAs/Al1-xGaxAs Bragg reflective layer and Al1-xGaxThe doping sources of the A upper limiting layer and the GaAs cap layer are both CBr4。
Example 5:
a method for preparing a high-power laser with an asymmetric structure and a bragg reflector, as shown in embodiment 3, except that H2The flow rate of (2) is 10000 sccm; the purity of TMGa is 99.9999 percent, and the temperature of a constant temperature bath of the TMGa is (-5) to 15 ℃; the purity of TMIn is 99.9999%, and the constant temperature of TMInThe temperature of the groove is 10-25 ℃; the purity of TMAl is 99.9999%, and the temperature of a thermostatic bath of TMAl is 10-25 ℃; AsH3The purity of (2) is 99.9999%; said Si2H6The purity of (2) is 99.9999%; the CBr4The temperature of the constant temperature bath is 10-25 ℃.
Example 6:
a method for preparing a high-power laser with an asymmetric structure and a bragg reflector, as shown in embodiment 3, except that in the step (2), the doping concentration in the GaAs buffer layer is 1E18 atoms/cm3；
Ga in step (3)1-xInxThe doping concentration of the P transition layer is 1E18 atoms/cm3The thickness was 0.2. mu.m, and x was 0.52.
Example 7:
a method for preparing a high-power laser with an asymmetric structure and a bragg reflector, as shown in embodiment 3, except that in the step (4), n-type Al is used1-xInxThe thickness of the P lower limiting layer is 1 μm, and the doping concentration is 1E18 atoms/cm3X is 0.5;
in the step (5), x is 0.5, y is 0.5, (Al)1-xGax)yIn1-yThe thickness of the P lower waveguide layer is 0.12 μm, and the intrinsic doping concentration is 1E16 atoms/cm3。
Example 8:
a method for preparing a high-power laser with an asymmetric structure and a bragg reflector, as shown in embodiment 3, except that in the step (6), Ga is added1-xInxThe thickness of the light emitting region of the P quantum well is 10nm, the P quantum well is not intentionally doped, and x is 0.45;
(Al) in step (7)1-xGax)yIn1-yThe thickness of the P upper waveguide layer is 0.07 μm, and the P upper waveguide layer is unintentionally doped with an intrinsic doping concentration of 1E16 atoms/cm3X is 0.5 and y is 0.5.
Example 9:
a method for preparing a high-power laser with an asymmetric structure and a bragg reflector, as shown in embodiment 3, except that in the step (8), Al is added1-xGaxAs/Al1-xGaxThe As Bragg reflector layer has x of 0.2, thickness of 0.2 μm, and doping concentration of 3E18 atoms/cm3；
X in the step (9) is 0.15, the thickness is 1 mu m, and the doping concentration is 1E19 atoms/cm3。
While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (9)

1. An asymmetric structure high-power laser with a Bragg reflector comprises a GaAs substrate and is characterized in that the GaAs substrate comprises a GaAs buffer layer and Ga which are deposited from bottom to top in sequence1-xInxP transition layer, Al1-xInxP lower limiting layer, (Al)1-xGax)yIn1-yP lower waveguide layer, Ga1-xInxP quantum well luminous zone, (Al)1-xGax)yIn1-yP upper waveguide layer, Al1-xGaxAs Bragg reflective layer and Al1-xGaxAn As upper limiting layer and a GaAs cap layer;
said (Al)1-xGax)yIn1-yThe thickness of the P lower waveguide layer is larger than that of the (Al)1-xGax)yIn1-yThe thickness of the P upper waveguide layer;
wherein Ga1-xInxX in the P transition layer is more than or equal to 0.45 and less than or equal to 0.55; al (Al)1-xInxX in the P lower limiting layer is more than or equal to 0.3 and less than or equal to 0.6; (Al)1- xGax)yIn1-yX is more than or equal to 0.4 and less than or equal to 0.6, and y is more than or equal to 0.4 and less than or equal to 0.6 in the P lower waveguide layer; ga1-xInxX in the P quantum well light-emitting region is more than or equal to 0.45 and less than or equal to 0.55; (Al)1-xGax)yIn1-yX is more than or equal to 0.4 and less than or equal to 0.6, and y is more than or equal to 0.4 and less than or equal to 0.6 in the P upper waveguide layer; al (Al)1-xGaxX in the As Bragg reflecting layer is more than or equal to 0 and less than or equal to 0.55; al (Al)1-xGaxX in the As upper limiting layer is more than or equal to 0.1 and less than or equal to 0.3.
2. A method for preparing an asymmetric structure high-power laser with a bragg reflector as claimed in claim 1, comprising the steps of:
(1) placing the GaAs substrate in MOCVD equipment, H2The environment is heated to 720 +/-10 ℃ and baked for 30 minutes, and AsH is introduced3Removing water and oxygen on the surface of the GaAs substrate to finish surface heat treatment;
(2) slowly reducing the temperature to 700 +/-10 ℃, and continuously introducing TMGa and AsH3Growing a GaAs buffer layer with the thickness of 0.3-1 mu m on the GaAs substrate;
(3) keeping the temperature at 700 +/-10 ℃, and continuously introducing TMIn, TMGa and PH3Growing Ga on the GaAs buffer layer of the step (2)1-xInxA P transition layer;
(4) keeping the temperature at 700 +/-10 ℃, and continuously introducing TMIn, TMAl and PH3Ga in step (3)1-xInxGrowing n-type Al on the P transition layer1-xInxA P lower limiting layer;
(5) the temperature is reduced to 650 +/-10 ℃, and TMIn, TMAl, TMGa and PH are continuously introduced3Al in step (4)1-xInxGrowth on P lower confinement layer (Al)1-xGax)yIn1-yA P lower waveguide layer;
(6) keeping the temperature at 650 +/-10 ℃, and continuously introducing TMIn, TMGa and PH3At step (5) (Al)1-xGax)yIn1-yGa growing on P lower waveguide layer1-xInxA P quantum well light emitting region;
(7) raising the temperature to 700 +/-10 ℃, and continuously introducing TMIn, TMAl, TMGa and PH3Ga in step (6)1-xInxGrowth on P quantum well light-emitting region (Al)1-xGax)yIn1-yA P upper waveguide layer;
(8) keeping the temperature at 700 +/-10 ℃, and continuously introducing TMAl, TMGa and AsH3(Al) at step (7)1-xGax)yIn1-yGrowing P-type Al on the P upper waveguide layer1-xGaxAs/Al1-xGaxThe number of the circulating logarithm of the As Bragg reflecting layer is z, and z is more than 0 and less than or equal to 100;
(9) keeping the temperature at 700 +/-10 ℃, and continuously introducing TMGa, TMAl and AsH in the step (8)3Growing Al on the Bragg reflection layer of the step (8)1-xGaxAn As upper confinement layer;
(10) reducing the temperature to 550 +/-10 ℃, closing TMAl, and continuously introducing TMGa and AsH3Al in step (9)1-xGaxGrowing a GaAs cap layer on the As upper limiting layer;
(11) and after the growth is finished, manufacturing a finished laser by adopting a packaging technology.
3. The method for preparing the asymmetric-structure high-power laser with the Bragg reflector as claimed in claim 2, wherein in the preparation process, the pressure of MOCVD equipment is 50-200 mbar;
the GaAs buffer layer and Al1-xInxThe N-type doping sources of the P lower limiting layer are all Si2H6(ii) a The Al is1-xGaxAs/Al1-xGaxAs Bragg reflective layer and Al1-xGaxThe doping sources of the A upper limiting layer and the GaAs cap layer are both CBr4；
H2The flow rate of the flow is 8000-50000 sccm; the purity of the TMGa is 99.9999%, and the temperature of a constant temperature bath of the TMGa is (-5) to 15 ℃; the purity of the TMIn is 99.9999%, and the temperature of a constant temperature bath of the TMIn is 10-25 ℃; the purity of the TMAl is 99.9999%, and the temperature of a constant temperature tank of the TMAl is 10-25 ℃; the AsH3The purity of (2) is 99.9999%; said Si2H6The purity of (2) is 99.9999%; the CBr4The temperature of the constant temperature bath is 10-25 ℃.
4. The method as claimed in claim 2, wherein the GaAs buffer layer has a thickness of 300-500nm and a doping concentration of 1E17-5E18 atoms/cm3；
Ga in step (3)1-xInxThe doping concentration of the P transition layer is 1E17-5E18 atoms/cm3The thickness was 0.2. mu.m.
5. The method for preparing an asymmetric high-power laser with a Bragg reflector as claimed in claim 2, wherein in the step (4), n-type Al1-xInxThe thickness of the P lower limiting layer is 0.5-2 μm, and the doping concentration is 1E17-5E18 atoms/cm3。
6. The method for preparing an asymmetric-structure high-power laser with a Bragg reflector as claimed in claim 2, wherein in the step (5) (Al)1-xGax)yIn1-yThe thickness of the lower waveguide layer under P is 0.1-0.2 μm, the lower waveguide layer is not intentionally doped, and the intrinsic doping concentration is 1E16-5E16 atoms/cm3。
7. The method for preparing an asymmetric-structure high-power laser with a Bragg reflector as claimed in claim 2, wherein in step (6), Ga is used1-xInxThe thickness of the light emitting region of the P quantum well is 5-15nm, and the light emitting region is not intentionally doped;
(Al) in step (7)1-xGax)yIn1-yThe thickness of the P upper waveguide layer is 0.05-0.15 μm, and the P upper waveguide layer is unintentionally doped with intrinsic doping concentration of 1E16-5E16 atoms/cm3。
8. The method for preparing the asymmetric-structure high-power laser with the Bragg reflector as claimed in claim 2, wherein in the step (8), z is 5-30;
the thickness of the Bragg reflection layer in the step (8) is 0.1-0.5 mu m, and the doping concentration is 1E18-5E18 atoms/cm3。
9. The method for preparing an asymmetric-structure high-power laser with a Bragg reflector as claimed in claim 2, wherein in step (9), the doping concentration of the AlGaAs upper cladding layer is 5E18-5E19 atoms/cm3；
The x of the step (9) is 0.15, and the thickness is 1 mu m.
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