Laser with light absorption loss suppression layer and preparation method thereof

Abstract

The present invention relates to a semiconductor optoelectronic device, and specifically discloses a laser with a light absorption loss suppression layer and a preparation method thereof. The single crystal nitride semiconductor laser with a light absorption loss suppression layer comprises, from bottom to top, a substrate, a lower cladding layer, a lower waveguide layer, an active layer, an upper waveguide layer, and an upper cladding layer, wherein a first light absorption loss suppression layer is provided between the lower cladding layer and the lower waveguide layer, and a second light absorption loss suppression layer is provided between the upper cladding layer and the upper waveguide layer, wherein the first light absorption loss suppression layer and the second light absorption loss suppression layer constitute a light absorption loss suppression layer; the single crystal nitride semiconductor laser with a light absorption loss suppression layer can improve the photoelectric conversion efficiency, suppress the internal optical loss of the laser, reduce the threshold current, improve the photoelectric conversion efficiency of the laser, and extend the service life of the laser.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor optoelectronic devices, and in particular relates to a laser with a light absorption loss suppression layer and a single crystal preparation method thereof. Background Art

[0002] Lasers are widely used in laser display, laser TV, laser projector, communication, medical treatment, weapons, guidance, ranging, spectral analysis, cutting, precision welding, high-density optical storage and other fields. There are many types of lasers, and the classification methods are also diverse. There are mainly solid, gas, liquid, semiconductor and dye types of lasers; compared with other types of lasers, all-solid-state semiconductor lasers have the advantages of small size, high efficiency, light weight, good stability, long life, simple and compact structure, and miniaturization. There are major differences between lasers and nitride semiconductor light-emitting diodes: 1) Lasers are generated by stimulated radiation of carriers, with a small half-width of the spectrum and high brightness. The output power of a single laser can be in the W level, while nitride semiconductor light-emitting diodes are spontaneously radiated, and the output power of a single light-emitting diode is in the mW level; 2) The operating current density of the laser reaches KA / cm 2 , which is more than 2 orders of magnitude higher than nitride light-emitting diodes, resulting in stronger electron leakage, more serious Auger recombination, stronger polarization effect, more serious electron-hole mismatch, and more serious efficiency attenuation Droop effect; 3) Light-emitting diodes spontaneously radiate incoherent light from high energy levels to low energy levels without external effects, while lasers radiate stimulated transitions. The energy of induced photons should be equal to the difference in energy levels of electron transitions, generating photons and induced photons that are completely coherent; 4) Different principles: Light-emitting diodes produce radiation recombination and luminescence under the action of external voltage when electron holes transition to quantum wells or pn junctions, while lasers require lasing conditions to be met before they can be lased. The carrier inversion distribution in the active region must be met. The stimulated radiation light oscillates back and forth in the resonant cavity, and the propagation in the gain medium amplifies the light. The threshold condition is met so that the gain is greater than the loss, and finally the laser is output.

[0003] Nitride semiconductor lasers have the following problems: internal optical absorption loss of the laser includes impurity absorption loss, carrier absorption loss, waveguide structure sidewall scattering loss and quantum well absorption loss; optical waveguide impurity absorption loss is high, which will compensate the acceptor and destroy the p-type in the p-type semiconductor, resulting in increased energy loss when the light is transmitted in the waveguide, which will affect the performance and efficiency of optical devices and reduce the transmission distance and quality of optical signals. Intrinsic carbon impurities, p-type doping has a low ionization rate (less than 10%), and a large amount of unionized Mg acceptor impurities (more than 90%) will produce a self-compensation effect and cause an increase in internal optical loss, resulting in a decrease in the slope efficiency of the laser and an increase in the threshold current, making the performance unstable or insufficient to meet the requirements of specific applications. It should also cause an increase in internal optical loss, resulting in a decrease in the slope efficiency of the laser and an increase in the threshold current. Summary of the invention

[0004] The purpose of the present invention is to provide a single crystal nitride semiconductor laser with a simple structure and reasonable design in order to solve the above problems.

[0005] The present invention achieves the above-mentioned purpose through the following technical solutions:

[0006] A laser with a light absorption loss suppression layer comprises, from bottom to top, a substrate, a lower cladding layer, a lower waveguide layer, an active layer, an upper waveguide layer, and an upper cladding layer, wherein a first light absorption loss suppression layer is provided between the lower cladding layer and the lower waveguide layer, a second light absorption loss suppression layer is provided between the upper cladding layer and the upper waveguide layer, and the first light absorption loss suppression layer and the second light absorption loss suppression layer constitute a light absorption loss suppression layer.

[0007] In a further optimized solution, the radiation recombination coefficient of the first light absorption loss suppression layer is v, and the radiation recombination coefficient of the second light absorption loss suppression layer is w, wherein: 5*10 -13 ≤w≤v≤5*10 -9 Unit: cm 3 / s;

[0008] The radiation recombination coefficient distribution of the first light absorption loss suppression layer has a function y=x -a The third quadrant curve distribution, wherein a>1 and is an odd number, the radiation recombination coefficient distribution of the second light absorption loss suppression layer has a function y=lnx curve distribution.

[0009] In a further optimized solution, the hole mobility of the first light absorption loss suppression layer is t, and the hole mobility of the second light absorption loss suppression layer is u, wherein: 5≤u≤t≤5000, in units of cm 2 / V / s;

[0010] The hole mobility distribution of the first light absorption loss suppression layer has a function y=x -b The third quadrant curve distribution, wherein b>1 and is an odd number, the hole mobility distribution of the second light absorption loss suppression layer has a function y=lnx curve distribution.

[0011] In a further optimized solution, the density of the first light absorption loss suppression layer is r, and the density of the second light absorption loss suppression layer is s, wherein: 1≤s≤r≤30, in units of g / cm 3 ;

[0012] The density distribution of the first light absorption loss suppression layer has a function y=x -c The third quadrant curve distribution, wherein c>1 and is an odd number, and the density distribution of the second light absorption loss suppression layer has a function y=lnx curve distribution.

[0013] In a further optimized solution, the radiation recombination coefficient distribution, hole mobility distribution and density distribution of the first light absorption loss suppression layer have the following relationship: 0<b<c<a<100.

[0014] In a further optimized solution, the light absorption coefficient of the first light absorption loss suppression layer is m, and the light absorption coefficient of the second light absorption loss suppression layer is n, wherein 0.2*10 5 ≤m≤n≤3*10 5 , unit is cm -1 ;

[0015] The light absorption coefficient of the first light absorption loss suppression layer has a function y=d x Curve distribution, wherein the light absorption coefficient distribution of the second light absorption loss suppression layer has a function y=g x Curved distribution, where 0<g<1<d, and d is an odd number.

[0016] In a further optimized scheme, the first light absorption loss suppression layer and the second light absorption loss suppression layer are any one or any combination of GaN, InGaN, InN, AlInN, AlGaN, AlInGaN, AlN, SiC, Ga2O3, BN, and diamond.

[0017] In a further optimized solution, the active layer is a periodic structure composed of a well layer and a barrier layer, the number of periods is 3≥m≥1, and the well layer is any of GaN, InGaN, InN, AlInN, AlGaN, AlInGaN, AlN, GaAs, GaP, InP, AlGaAs, AlInGaAs, AlGaInP, InGaAs, InGaAsN, AlInAs, AlInP, AlGaP, InGaP, GaSb, InSb, InAs, InAsSb, AlGaSb, AlSb, InGaSb, AlGaAsSb, InGaAsSb, SiC, Ga2O3, BN, and diamond. One or any combination thereof, with a thickness of 10 to 100 angstroms, and the barrier layer is any one or any combination of GaN, InGaN, InN, AlInN, AlGaN, AlInGaN, AlN, GaAs, GaP, InP, AlGaAs, AlInGaAs, AlGaInP, InGaAs, InGaAsN, AlInAs, AlInP, AlGaP, InGaP, GaSb, InSb, InAs, InAsSb, AlGaSb, AlSb, InGaSb, AlGaAsSb, InGaAsSb, SiC, Ga2O3, BN, and diamond, with a thickness of 10 to 150 angstroms;

[0018] The lower cladding layer, the lower waveguide layer, the upper waveguide layer, and the upper cladding layer are any one or any combination of GaN, InGaN, InN, AlInN, AlGaN, AlInGaN, AlN, GaAs, GaP, InP, AlGaAs, AlInGaAs, AlGaInP, InGaAs, InGaAsN, AlInAs, AlInP, AlGaP, InGaP, GaSb, InSb, InAs, InAsSb, AlGaSb, AlSb, InGaSb, AlGaAsSb, InGaAsSb, SiC, Ga2O3, BN, and diamond;

[0019] The substrate is a single crystal substrate, including any one of sapphire, silicon, Ge, SiC, AlN, GaN, GaAs, InP, InAs, GaSb, sapphire / SiO2 composite substrate, Mo, TiW, CuW, Cu, sapphire / AlN composite substrate, diamond, sapphire / SiNx composite substrate, sapphire / SiO2 / SiNx composite substrate, MgAl2O4, MgO, ZnO, ZrB2, LiAlO2 and LiGaO2 composite substrate.

[0020] A method for preparing a single crystal of a laser having a light absorption loss suppression layer, wherein the single crystal preparation method of the substrate adopts a multi-step method for growth, specifically comprising the following steps:

[0021] S1: epitaxially grow a seed crystal layer in a MOCVD metal organic chemical vapor epitaxy reaction chamber using a sapphire substrate;

[0022] S2: placing the seed layer into a HVPE or CVD reaction chamber to grow a single crystal GaN thick film;

[0023] S3: GaN is peeled off sapphire by stress self-separation or laser lift-off technology to form a GaN single crystal substrate with a defect density of less than or equal to 5E6cm -2 ;

[0024] S4: transferring the single crystal substrate into a reaction chamber of MOCVD metal organic chemical vapor phase epitaxy, and growing a single crystal of a lower cladding layer by using MOCVD metal organic chemical vapor phase epitaxy;

[0025] S5: growing a first light absorption loss suppression layer on the lower cladding layer using MOCVD;

[0026] S6: epitaxially growing a lower waveguide layer, an active layer, and an upper waveguide layer on the first light absorption loss suppression layer by using MOCVD;

[0027] S7: growing a second light absorption loss suppression layer on the upper waveguide layer using MOCVD;

[0028] S8: epitaxially growing an upper cladding layer on the second light absorption loss suppression layer using MOCVD.

[0029] As a further optimization scheme, in step S1: the seed layer includes a multilayer GaN, the multilayer GaN includes a GaN buffer layer grown at 500-900°C, a pressure of 100-500 Torr, a rotation speed of 600-12000 rpm, and a thickness of 10-200 nm, a GaN three-dimensional growth layer grown at 900-1100°C, a pressure of 150-500 Torr, a rotation speed of 600-12000 rpm, and a thickness of 200-5000 nm, and a GaN two-dimensional growth layer grown at 1000-1200°C, a pressure of 150-250 Torr, a rotation speed of 600-12000 rpm, and a thickness of 2000-10000 nm;

[0030] In step S2: the temperature is 1000-1200°C, HCl and GaCl3 are introduced into the reaction chamber as gallium sources, NH3 is a nitrogen source, and the thickness is 5-500um;

[0031] In step S4: the growth temperature is 1000-1200°C, the growth pressure is 100-300 Torr, the reaction elements are TMGa, TEGa, TMAl, TMIn, NH3, N2, H2, the rotation speed is 1000-1300 rpm, the growth rate is 0.2-3 um / h, the V / III ratio is 100-80000, and the doping element is any one of SiH4 or disilane. The lower cladding layer is first grown on the substrate by controlling the temperature, pressure, reaction element selection and ratio, rotation speed, growth rate, V / III ratio, and a suitable combination of doping elements;

[0032] In step S5: the growth temperature is 1000-1150°C, the growth pressure is 100-200 Torr, the reaction elements are TMGa, TEGa, TMAl, TMIn, NH3, N2, H2, the rotation speed is 1000-1300 rpm, the growth rate is 0.5-5um / h, the V / III ratio is 100-80000, and the doping element is any one of SiH4 or disilane. By controlling the temperature, pressure, reaction element selection and ratio, rotation speed, growth rate, V / III ratio, and appropriate combination of doping elements, a first light absorption loss suppression layer is first grown on the substrate, and by controlling the Al atom injection curve to be y=p x (p>1) The radiation recombination coefficient distribution of the first light absorption loss suppression layer has a function y=x -a (a>1 and is an odd number) the third quadrant curve distribution;

[0033] By controlling the Al atom injection curve to y=P x (P>1) makes the light absorption coefficient have the function y=d x (d>1) curvilinear distribution;

[0034] By controlling the Al / Ga element ratio, the curve changes to y=q x (q>1) makes the hole mobility distribution of the first light absorption loss suppression layer have a function y=x -b (b>1 and is an odd number) the third quadrant curve distribution;

[0035] By controlling the Al / Ga element ratio, the curve changes to y=Q x (Q>1) density distribution has function y=x -c (c>1 and is an odd number) the third quadrant curve distribution;

[0036] In step S6: the growth conditions of the lower waveguide layer are as follows: the growth temperature is 650-1000° C., the growth pressure is 100-300 Torr, the reaction elements are TMGa, TEGa, TMAl, TMIn, NH3, N2, H2, the rotation speed is 400-900 rpm, the growth rate is 0.05-2 um / h, the V / III ratio is 1000-90000, and the doping element is any one of SiH4 and disilane. The lower waveguide layer is first grown on the substrate by controlling the temperature, pressure, reaction element selection and ratio, rotation speed, growth rate, V / III ratio, and a suitable combination of doping elements;

[0037] The growth conditions of the active layer are as follows: the growth temperature is 600-950°C, the growth pressure is 100-250 Torr, the reaction elements are TEGa, TMAl, TMIn, NH3, N2, H2, the rotation speed is 300-800 revolutions, the growth rate is 0.002-2um / h, the V / III ratio is 1000-90000, and the doping element is any one of SiH4 or disilane. The active layer is first grown on the substrate by controlling the temperature, pressure, reaction element selection and ratio, rotation speed, growth rate, V / III ratio, and a suitable combination of doping elements;

[0038] The growth conditions of the upper waveguide layer are as follows: the growth temperature is 650-1000°C, the growth pressure is 100-300 Torr, the reaction elements are TMGa, TEGa, TMAl, TMIn, NH3, N2, H2, the rotation speed is 400-900 revolutions, the growth rate is 0.05-2um / h, the V / III ratio is 1000-90000, and the doping element is any one of SiH4 or disilane. The lower waveguide layer is first grown on the substrate by controlling the temperature, pressure, reaction element selection and ratio, rotation speed, growth rate, V / III ratio, and a suitable combination of doping elements;

[0039] In step S7:

[0040] The growth temperature is 800-1050°C, the growth pressure is 100-200Torr, the reaction elements are TMGa, TEGa, TMAl, TMIn, NH3, N2, H2, the rotation speed is 900-1300 rpm, the growth rate is 0.5-5um / h, the V / III ratio is 200-80000, and the doping element is any one of SiH4, disilane or Cp2Mg. By controlling the temperature, pressure, reaction element selection and ratio, rotation speed, growth rate, V / III ratio, and appropriate combination of doping elements, a second light absorption loss suppression layer is first grown on the substrate, and by controlling the Al atom injection curve to y=j x (0<j<1) curve distribution makes the radiation recombination coefficient distribution of the second light absorption loss suppression layer have a function y=lnx curve distribution;

[0041] By controlling the Al atom implantation curve to be y=J x The (0<J<1) curve distribution makes the light absorption coefficient distribution of the second light absorption loss suppression layer have a function y=g x (0<g<1) curve distribution;

[0042] By controlling the Al / Ga element ratio, the curve changes to y=k x (0<k<1) makes the hole mobility distribution of the second light absorption loss suppression layer have a function y=lnx curve distribution;

[0043] By controlling the Al / Ga element ratio, the curve changes to y=K x (0<K<1) makes the density distribution of the second light absorption loss suppression layer have a function y=lnx curve distribution.

[0044] The beneficial effects of the present invention are as follows: the present invention arranges a first light absorption loss suppression layer between the lower cladding layer and the lower waveguide layer, arranges a second light absorption loss suppression layer between the upper cladding layer and the upper waveguide layer, and regulates the radiation recombination coefficient and its distribution of the light absorption loss suppression layer, the hole concentration and its distribution injected into the active layer, the laser density distribution, and the laser light field distribution to reduce the internal optical loss of carrier absorption loss, improve the photoelectric conversion efficiency, suppress the internal optical loss of the laser, reduce the threshold current, improve the photoelectric conversion efficiency of the laser, and extend the service life of the laser. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a SIMS secondary ion mass spectrum of a laser having a light absorption loss suppression layer according to the present invention;

[0046] Figure 2 It is a schematic structural diagram of a laser having a light absorption loss suppression layer according to the present invention;

[0047] Figure 3 This is a SIMS secondary ion mass spectrum (partially enlarged view) of a laser with a light absorption loss suppression layer of the present invention.

[0048] In the figure: 100, substrate; 101, lower cladding layer; 102, lower waveguide layer; 103, active layer; 104, upper waveguide layer; 105, upper cladding layer; 106, light absorption loss suppression layer; 106a, first light absorption loss suppression layer; 106b, second light absorption loss suppression layer. DETAILED DESCRIPTION

[0049] The present application is further described in detail below in conjunction with the accompanying drawings. It is necessary to point out here that the following specific implementation methods are only used to further illustrate the present application and cannot be understood as limiting the scope of protection of the present application. Technical personnel in this field can make some non-essential improvements and adjustments to the present application based on the above application content.

[0050] like Figure 1-Figure 3 As shown, a laser with a light absorption loss suppression layer comprises, from bottom to top, a substrate 100, a lower cladding layer 101, a lower waveguide layer 102, an active layer 103, an upper waveguide layer 104, and an upper cladding layer 105, wherein a first light absorption loss suppression layer 106a is provided between the lower cladding layer 101 and the lower waveguide layer 102, a second light absorption loss suppression layer 106b is provided between the upper cladding layer 105 and the upper waveguide layer 104, and the first light absorption loss suppression layer 106a and the second light absorption loss suppression layer 106b constitute the light absorption loss suppression layer 106.

[0051] Among them, the design of the first light absorption loss suppression layer 106a and the second light absorption loss suppression layer 106b can help improve the performance and efficiency of optical devices, reduce energy loss during the transmission of optical signals, and thus improve the performance and reliability of the devices. This layer is usually composed of materials whose optical properties can effectively suppress the absorption of light to ensure that the optical signal can be effectively transmitted in the waveguide without excessive losses.

[0052] In a further optimized solution, the radiation recombination coefficient of the first light absorption loss suppression layer 106a is v, and the radiation recombination coefficient of the second light absorption loss suppression layer 106b is w, wherein: 5*10 -13 ≤w≤v≤5*10 -9 Unit: cm 3 / s;

[0053] In semiconductor physics, the radiative recombination coefficient describes the probability of recombination between charge carriers (such as electrons and holes) through radiation. When electrons and holes meet and recombine, they release energy in the form of radiation, producing photons. The radiative recombination coefficient represents the contribution of each charge carrier to radiative recombination per unit time.

[0054] The radiation recombination coefficient distribution of the first light absorption loss suppression layer 106a has a function y=x -a The third quadrant curve distribution, wherein a>1 and is an odd number, the radiation recombination coefficient distribution of the second light absorption loss suppression layer 106b has a function y=lnx curve distribution, which regulates the radiation recombination coefficient and its distribution of the light absorption loss suppression layer, improves the quantum confinement efficiency and stimulated radiation efficiency, reduces the non-radiative recombination probability such as Auger recombination, thereby reducing the internal optical loss of quantum well absorption loss and improving the photoelectric conversion efficiency;.

[0055] In a further optimized solution, the hole mobility of the first light absorption loss suppression layer 106a is t, and the hole mobility of the second light absorption loss suppression layer 106b is u, wherein: 5≤u≤t≤5000, in units of cm 2 / V / s;

[0056] Hole mobility refers to the rate or ability of holes to move under an applied electric field in a semiconductor. Materials with high mobility help improve the performance of semiconductor devices because they can more efficiently transfer charges, thereby improving the response speed and efficiency of the device.

[0057] The hole mobility distribution of the first light absorption loss suppression layer 106a has a function y=x -b The third quadrant curve distribution, wherein b>1 and is an odd number, the hole mobility distribution of the second light absorption loss suppression layer 106b has a function y=lnx curve distribution, which regulates the hole concentration and distribution of the injected active layer, quantizes the energy of the injected hole carriers, fills the sub-bands step by step, improves the matching degree of the electron-hole wave function of the active layer, improves the utilization rate of the electron holes injected into the active layer, reduces the internal optical loss of the carrier absorption loss, increases the differential gain, accelerates the particle number inversion of the laser, and reduces the threshold current density.

[0058] In a further optimized solution, the density of the first light absorption loss suppression layer 106a is r, and the density of the second light absorption loss suppression layer 106b is s, wherein: 1≤s≤r≤30, in units of g / cm 3 ;

[0059] Density distribution usually refers to the change in the concentration of carriers (such as electrons or holes) with the change of spatial position.

[0060] The density distribution of the first light absorption loss suppression layer 106a has a function y=x -c The third quadrant curve distribution, where c>1 and is an odd number, the density distribution of the second light absorption loss suppression layer 106b has a function y=lnx curve distribution, which regulates the laser density distribution, increases the steepness of the interface, reduces the interface state density of the waveguide layer interface, reduces the internal optical loss of the waveguide structure side wall scattering loss, and improves the photoelectric conversion efficiency.

[0061] In a further optimized solution, the radiation recombination coefficient distribution, hole mobility distribution and density distribution of the first light absorption loss suppression layer 106a have the following relationship: 0<b<c<a<100.

[0062] In a further optimized solution, the light absorption coefficient of the first light absorption loss suppression layer 106a is m, and the light absorption coefficient of the second light absorption loss suppression layer 106b is n, wherein 0.2*10 5 ≤m≤n≤3*10 5 , unit is cm -1 ;

[0063] The light absorption coefficient of the first light absorption loss suppression layer 106a has a function y=d x Curve distribution, wherein the light absorption coefficient distribution of the second light absorption loss suppression layer 106b has a function y=g x The curve distribution, where 0<g<1<d, and d is an odd number, regulates the light field distribution of the laser, reduces the longitudinal diffusion of the light field, isolates the absorption loss of the electron blocking layer and the unionized Mg acceptor of the upper cladding layer to the light field, reduces the recombination of carriers with the heterojunction interface state and surface state, inhibits the internal optical loss of the laser, reduces the threshold current, and improves the photoelectric conversion efficiency of the laser.

[0064] In a further optimized solution, the first light absorption loss suppression layer 106a and the second light absorption loss suppression layer 106b are any one or any combination of GaN, InGaN, InN, AlInN, AlGaN, AlInGaN, AlN, SiC, Ga2O3, BN, and diamond.

[0065] like Figure 1As shown, in a further optimized solution, the active layer 103 is a periodic structure composed of a well layer and a barrier layer, the number of periods is 3≥m≥1, and the well layer is GaN, InGaN, InN, AlInN, AlGaN, AlInGaN, AlN, GaAs, GaP, InP, AlGaAs, AlInGaAs, AlGaInP, InGaAs, InGaAsN, AlInAs, AlInP, AlGaP, InGaP, GaSb, InSb, InAs, InAsSb, AlGaSb, AlSb, InGaSb, AlGaAsSb, InGaAsSb, SiC, Ga2O3, BN, diamond any one or any combination thereof, with a thickness of 10 to 100 angstroms; the barrier layer is any one or any combination of GaN, InGaN, InN, AlInN, AlGaN, AlInGaN, AlN, GaAs, GaP, InP, AlGaAs, AlInGaAs, AlGaInP, InGaAs, InGaAsN, AlInAs, AlInP, AlGaP, InGaP, GaSb, InSb, InAs, InAsSb, AlGaSb, AlSb, InGaSb, AlGaAsSb, InGaAsSb, SiC, Ga2O3, BN, and diamond, with a thickness of 10 to 150 angstroms;

[0066] like Figure 1 As shown, the lower cladding layer 101, the lower waveguide layer 102, the upper waveguide layer 104, and the upper cladding layer 105 are any one or any combination of GaN, InGaN, InN, AlInN, AlGaN, AlInGaN, AlN, GaAs, GaP, InP, AlGaAs, AlInGaAs, AlGaInP, InGaAs, InGaAsN, AlInAs, AlInP, AlGaP, InGaP, GaSb, InSb, InAs, InAsSb, AlGaSb, AlSb, InGaSb, AlGaAsSb, InGaAsSb, SiC, Ga2O3, BN, and diamond;

[0067] The substrate 100 is a single crystal substrate, including any one of sapphire, silicon, Ge, SiC, AlN, GaN, GaAs, InP, InAs, GaSb, sapphire / SiO2 composite substrate 100, Mo, TiW, CuW, Cu, sapphire / AlN composite substrate, diamond, sapphire / SiNx composite substrate, sapphire / SiO2 / SiNx composite substrate, MgAl2O4, MgO, ZnO, ZrB2, LiAlO2 and LiGaO2 composite substrate.

[0068] The laser element is tested with laser chip testing equipment. The laser element is designed with a ridge width of 45um and a cavity length of 1200um. The test current is 0~4A ampere pulse or continuous mode test. The test environment temperature is 25℃. The laser light power signal is collected by an integrating sphere to test the photoelectric conversion efficiency, thermal attenuation (after To packaging, placed in the air, the ambient temperature is 25℃, and tested continuously for 60 seconds without a heat sink, and the power difference between the test and 0 seconds), internal optical loss and threshold current density (the threshold current density is the starting current density of the laser lasing).

[0069] The structure of a traditional laser element includes, from bottom to top, a substrate, a lower cladding layer, a lower wave layer, an active layer, an upper waveguide layer, and an upper cladding layer.

[0070] The structure of the laser element includes, from bottom to top, a substrate, a lower cladding layer, a first light absorption loss suppression layer, a lower wave layer, an active layer, an upper waveguide layer, a second light absorption loss suppression layer, and an upper cladding layer.

[0071] In order to highlight the technical advantages of the present technical solution, this embodiment compares the performance of the laser element proposed by the present invention with that of a traditional laser element. The comparison results can be seen in Table 1.

[0072] Table 1

[0073] By comparison, it can be found that the single crystal nitride semiconductor laser with a light absorption loss suppression layer proposed in the present invention has a thermal attenuation reduced from 84% to 36%, a reduction of 57%, compared with the traditional laser. By reducing the thermal attenuation, the aging speed of the device can be slowed down, the service life of the device can be extended, and the stability of the device in different environments and the working efficiency of the device can be improved, making it more energy-saving. At the same time, the additional heat dissipation demand can be reduced, thereby reducing power consumption; the photoelectric conversion efficiency is increased from 41% to 53%, an increase of 29%; the internal optical loss is reduced from 11.6cm -1 Lowered to 7.3cm -1 ;Threshold current density from 2.13kA / cm 2 Reduced to 0.91 kA / cm 2 .

[0074] A method for preparing a single crystal of a laser having a light absorption loss suppression layer, wherein the single crystal preparation method of the substrate 100 is grown by a multi-step method, specifically comprising the following steps:

[0075] S1: epitaxially growing a seed crystal layer in a MOCVD metal organic chemical vapor epitaxy reaction chamber using a sapphire substrate 100;

[0076] S2: placing the seed layer into a HVPE or CVD reaction chamber to grow a single crystal GaN thick film;

[0077] S3: The GaN is stripped off the sapphire by stress self-separation or laser stripping technology to form a GaN single crystal substrate 100, with a defect density of less than or equal to 5E6cm -2 ;

[0078] S4: introducing the single crystal substrate 100 into a reaction chamber of a MOCVD metal organic chemical vapor phase epitaxy, and using MOCVD metal organic chemical vapor phase epitaxy to perform single crystal growth of a lower cladding layer 101;

[0079] S5: growing a first light absorption loss suppression layer 106 a on the lower cladding layer 101 using MOCVD;

[0080] S6: epitaxially growing the lower waveguide layer 102, the active layer 103 and the upper waveguide layer 104 on the first light absorption loss suppression layer 106a by using MOCVD;

[0081] S7: growing a second light absorption loss suppression layer 106 b on the upper waveguide layer 104 using MOCVD;

[0082] S8: epitaxially grow an upper cladding layer on the second light absorption loss suppression layer 106 b using MOCVD.

[0083] Among them, MOCVD is a new type of vapor phase epitaxial growth technology developed on the basis of vapor phase epitaxy (VPE). Specifically, MOCVD uses organic compounds of group III and group II elements and hydrides of group V and VI elements as crystal growth source materials, and performs vapor phase epitaxy on the substrate 100 in a thermal decomposition reaction mode to grow thin-layer single crystal materials of various group III-V, group II-VI compound semiconductors and their multi-component solid solutions;

[0084] HVPE is a semiconductor growth technology, which stands for "Hydride Vapor Phase Epitaxy". In the HVPE process, semiconductor materials are usually deposited on the surface of the substrate 100 by reacting hydrogen in the gas with metal organic compounds at high temperature. This technology is usually used to grow III-V compound semiconductor materials, such as gallium nitride, aluminum nitride, etc.

[0085] CVD is a commonly used semiconductor manufacturing process, which stands for "Chemical Vapor Deposition". In the CVD process, a gaseous precursor is introduced into a reaction chamber and deposited on the surface of the substrate 100 to form a thin film or coating under appropriate temperature and pressure.

[0086] As a further optimization scheme, in step S1: the seed layer includes a multilayer GaN, the multilayer GaN includes a GaN buffer layer grown at 500-900°C, a pressure of 100-500 Torr, a rotation speed of 600-12000 rpm, and a thickness of 10-200 nm, a GaN three-dimensional growth layer grown at 900-1100°C, a pressure of 150-500 Torr, a rotation speed of 600-12000 rpm, and a thickness of 200-5000 nm, and a GaN two-dimensional growth layer grown at 1000-1200°C, a pressure of 150-250 Torr, a rotation speed of 600-12000 rpm, and a thickness of 2000-10000 nm;

[0087] The rotation speed refers to the rotation speed of the substrate during the growth process, which can affect the uniformity and thickness of the growth layer.

[0088] In step S2: the temperature is 1000-1200°C, HCl and GaCl3 are introduced into the reaction chamber as gallium sources, NH3 is a nitrogen source, and the thickness is 5-500um;

[0089] In step S4: the growth temperature is 1000-1200° C., the growth pressure is 100-300 Torr, the reaction elements are TMGa, TEGa, TMAl, TMIn, NH3, N2, H2, the rotation speed is 1000-1300 rpm, the growth rate is 0.2-3 um / h, the V / III ratio is 100-80000, and the doping element is any one of SiH4 or disilane. The lower cladding layer 101 is grown on the substrate 100 by controlling the temperature, pressure, reaction element selection and ratio, rotation speed, growth rate, V / III ratio, and a suitable combination of doping elements;

[0090] In step S5: the growth temperature is 1000-1150° C., the growth pressure is 100-200 Torr, the reaction elements are TMGa, TEGa, TMAl, TMIn, NH3, N2, H2, the rotation speed is 1000-1300 rpm, the growth rate is 0.5-5 um / h, the V / III ratio is 100-80000, and the doping element is any one of SiH4 and disilane. The first light absorption loss suppression layer 106a is grown on the substrate 100 by controlling the temperature, pressure, reaction element selection and ratio, rotation speed, growth rate, V / III ratio, and a suitable combination of doping elements, as shown in FIG. Figure 3 As shown, by controlling the Al atom injection curve to y=p x (p>1) The radiation recombination coefficient distribution of the first light absorption loss suppression layer 106a has a function y=x -a(a>1 and is an odd number) The third quadrant curve distribution regulates the radiation recombination coefficient and its distribution of the light absorption loss suppression layer, improves the quantum confinement efficiency and stimulated radiation efficiency, reduces the probability of non-radiative recombination such as Auger recombination, thereby reducing the internal optical loss of quantum well absorption loss and improving the photoelectric conversion efficiency;

[0091] By controlling the Al atom injection curve to y=P x (P>1) The light absorption coefficient has the function y=d x (d>1) curve distribution, regulate the light field distribution of the laser, reduce the longitudinal diffusion of the light field, isolate the absorption loss of the light field by the unionized Mg acceptor in the electron blocking layer and the upper cladding layer, reduce the recombination of carriers with the interface state and surface state of the heterojunction, inhibit the internal optical loss of the laser, reduce the threshold current, and improve the photoelectric conversion efficiency of the laser;

[0092] By controlling the Al / Ga element ratio, the curve changes to y=q x (q>1) makes the hole mobility distribution of the first light absorption loss suppression layer 106a have a function y=x -b (b>1 and is an odd number) The third quadrant curve distribution regulates the hole concentration and distribution injected into the active layer, quantizes the energy of the injected hole carriers, fills the sub-bands step by step, improves the matching degree of the electron-hole wave function of the active layer, improves the utilization rate of the electron holes injected into the active layer, reduces the internal optical loss of carrier absorption loss, increases the differential gain, accelerates the particle number inversion of the laser, and reduces the threshold current density;

[0093] By controlling the Al / Ga element ratio, the curve changes to y=Q x (Q>1) density distribution has function y=x -c (c>1 and is an odd number) The third quadrant curve distribution regulates the laser density distribution, improves the steepness of the interface, reduces the interface state density of the waveguide layer interface, reduces the internal optical loss of the waveguide structure side wall scattering loss, and improves the photoelectric conversion efficiency;

[0094] In step S6: the growth conditions of the lower waveguide layer 102 are as follows: the growth temperature is 650-1000° C., the growth pressure is 100-300 Torr, the reaction elements are TMGa, TEGa, TMAl, TMIn, NH3, N2, H2, the rotation speed is 400-900 rpm, the growth rate is 0.05-2 um / h, the V / III ratio is 1000-90000, and the doping element is any one of SiH4 and disilane. The lower waveguide layer 102 is grown on the substrate 100 by controlling the temperature, pressure, reaction element selection and ratio, rotation speed, growth rate, V / III ratio, and a suitable combination of doping elements;

[0095] The growth conditions of the active layer 103 are as follows: the growth temperature is 600-950° C., the growth pressure is 100-250 Torr, the reaction elements are TEGa, TMAl, TMIn, NH 3 , N 2 , H 2 , the rotation speed is 300-800 rpm, the growth rate is 0.002-2 um / h, the V / III ratio is 1000-90000, and the doping element is any one of SiH 4 and disilane. The active layer 103 is grown on the substrate 100 by controlling the temperature, pressure, reaction element selection and ratio, rotation speed, growth rate, V / III ratio, and a suitable combination of doping elements;

[0096] The growth conditions of the upper waveguide layer 104 are as follows: the growth temperature is 650-1000° C., the growth pressure is 100-300 Torr, the reaction elements are TMGa, TEGa, TMAl, TMIn, NH3, N2, H2, the rotation speed is 400-900 rpm, the growth rate is 0.05-2 um / h, the V / III ratio is 1000-90000, and the doping element is any one of SiH4 or disilane. The lower waveguide layer 102 is grown on the substrate 100 by controlling the temperature, pressure, reaction element selection and ratio, rotation speed, growth rate, V / III ratio, and a suitable combination of doping elements;

[0097] In step S7:

[0098] The growth temperature is 800-1050°C, the growth pressure is 100-200Torr, the reaction elements are TMGa, TEGa, TMAl, TMIn, NH3, N2, H2, the rotation speed is 900-1300 rpm, the growth rate is 0.5-5um / h, the V / III ratio is 200-80000, and the doping element is any one of SiH4, disilane, or Cp2Mg. By controlling the temperature, pressure, reaction element selection and ratio, rotation speed, growth rate, V / III ratio, and appropriate combination of doping elements, the second light absorption loss suppression layer 106b is first grown on the substrate 100, as shown in FIG. Figure 3 As shown, by controlling the Al atom injection curve to y=j x (0<j<1) curve distribution makes the radiation recombination coefficient distribution of the second light absorption loss suppression layer 106b have a function y=lnx curve distribution, regulates the radiation recombination coefficient and its distribution of the light absorption loss suppression layer, improves the quantum confinement efficiency and stimulated radiation efficiency, reduces the non-radiative recombination probability such as Auger recombination, thereby reducing the internal optical loss of quantum well absorption loss and improving the photoelectric conversion efficiency;

[0099] By controlling the Al atom implantation curve to be y=J x The (0<J<1) curve distribution makes the light absorption coefficient distribution of the second light absorption loss suppression layer 106b have a function y=g xThe (0<g<1) curve distribution regulates the light field distribution of the laser, reduces the longitudinal diffusion of the light field, isolates the absorption loss of the light field by the unionized Mg acceptor in the electron blocking layer and the upper cladding layer, reduces the recombination of carriers with the heterojunction interface state and surface state, suppresses the internal optical loss of the laser, reduces the threshold current, and improves the photoelectric conversion efficiency of the laser;

[0100] By controlling the Al / Ga element ratio, the curve changes to y=k x (0<k<1) makes the hole mobility distribution of the second light absorption loss suppression layer 106b have a function y=lnx curve distribution, regulates the hole concentration and its distribution injected into the active layer, quantizes the energy of the injected hole carriers, fills the sub-bands step by step, improves the matching degree of the electron-hole wave function of the active layer, improves the utilization rate of the electron holes injected into the active layer, reduces the internal optical loss of the carrier absorption loss, increases the differential gain, accelerates the particle number inversion of the laser, and reduces the threshold current density;

[0101] By controlling the Al / Ga element ratio, the curve changes to y=K x (0<K<1) makes the density distribution of the second light absorption loss suppression layer 106b have a function y=lnx curve distribution, regulates the laser density distribution, improves the steepness of the interface, reduces the interface state density of the waveguide layer interface, reduces the internal optical loss of the side wall scattering loss of the waveguide structure, and improves the photoelectric conversion efficiency.

[0102] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A laser having a light absorption loss suppression layer, comprising, from bottom to top, a substrate, a lower cladding layer, a lower waveguide layer, an active layer, an upper waveguide layer, and an upper cladding layer, characterized in that: A first light absorption loss suppression layer is provided between the lower cladding layer and the lower waveguide layer, and a second light absorption loss suppression layer is provided between the upper cladding layer and the upper waveguide layer, wherein the first light absorption loss suppression layer and the second light absorption loss suppression layer constitute a light absorption loss suppression layer; The radiation recombination coefficient of the first light absorption loss suppression layer is v, and the radiation recombination coefficient of the second light absorption loss suppression layer is w, where: 5*10 -13 ≤w≤v≤5*10 -9 , unit is cm 3 / s; The radiation recombination coefficient distribution of the first light absorption loss suppression layer has a function y=x -a The third quadrant curve distribution, wherein a>1 and is an odd number, wherein x is the depth of the first light absorption loss suppression layer to the lower cladding layer; the radiation recombination coefficient distribution of the second light absorption loss suppression layer has a function y=lnx curve distribution, wherein x is the depth of the upper cladding layer to the second light absorption loss suppression layer; The hole mobility of the first light absorption loss suppression layer is t, and the hole mobility of the second light absorption loss suppression layer is u, wherein: 5≤u≤t≤5000, in units of cm 2 / V / s; The hole mobility distribution of the first light absorption loss suppression layer has a function y=x -b The third quadrant curve distribution, wherein b>1 and is an odd number, the hole mobility distribution of the second light absorption loss suppression layer has a function y=lnx curve distribution; The density of the first light absorption loss suppression layer is r, and the density of the second light absorption loss suppression layer is s, wherein: 1≤s≤r≤30, the unit is g / cm 3 ; The density distribution of the first light absorption loss suppression layer has a function y=x -c The third quadrant curve distribution, wherein c>1 and is an odd number, and the density distribution of the second light absorption loss suppression layer has a function y=lnx curve distribution.

2. The laser having a light absorption loss suppression layer according to claim 1, characterized in that: The radiation recombination coefficient distribution, hole mobility distribution and density distribution of the first light absorption loss suppression layer have the following relationship: 0<b<c<a<100.

3. The laser having a light absorption loss suppression layer according to claim 2, characterized in that: The light absorption coefficient of the first light absorption loss suppression layer is m, and the light absorption coefficient of the second light absorption loss suppression layer is n, wherein 0.2*10 5 ≤m≤n≤3*10 5 , unit is cm -1 ; The light absorption coefficient of the first light absorption loss suppression layer has a function y=d x Curve distribution, wherein the light absorption coefficient distribution of the second light absorption loss suppression layer has a function y=g x Curved distribution, where 0<g<1<d, and d is an odd number.

4. The laser having a light absorption loss suppression layer according to claim 3, characterized in that: The first light absorption loss suppression layer and the second light absorption loss suppression layer are any one or any combination of GaN, InGaN, InN, AlInN, AlGaN, AlInGaN, AlN, SiC, Ga2O3, BN, and diamond.

5. A laser having a light absorption loss suppression layer according to any one of claim 4, characterized in that: The active layer is a periodic structure composed of a well layer and a barrier layer, the number of periods is 3≥m≥1, and the well layer is any one or any of GaN, InGaN, InN, AlInN, AlGaN, AlInGaN, AlN, GaAs, GaP, InP, AlGaAs, AlInGaAs, AlGaInP, InGaAs, InGaAsN, AlInAs, AlInP, AlGaP, InGaP, GaSb, InSb, InAs, InAsSb, AlGaSb, AlSb, InGaSb, AlGaAsSb, InGaAsSb, SiC, Ga2O3, BN, and diamond. combination, with a thickness of 10 to 100 angstroms, and the barrier layer is any one or any combination of GaN, InGaN, InN, AlInN, AlGaN, AlInGaN, AlN, GaAs, GaP, InP, AlGaAs, AlInGaAs, AlGaInP, InGaAs, InGaAsN, AlInAs, AlInP, AlGaP, InGaP, GaSb, InSb, InAs, InAsSb, AlGaSb, AlSb, InGaSb, AlGaAsSb, InGaAsSb, SiC, Ga2O3, BN, and diamond, with a thickness of 10 to 150 angstroms; The lower cladding layer, the lower waveguide layer, the upper waveguide layer, and the upper cladding layer are any one or any combination of GaN, InGaN, InN, AlInN, AlGaN, AlInGaN, AlN, GaAs, GaP, InP, AlGaAs, AlInGaAs, AlGaInP, InGaAs, InGaAsN, AlInAs, AlInP, AlGaP, InGaP, GaSb, InSb, InAs, InAsSb, AlGaSb, AlSb, InGaSb, AlGaAsSb, InGaAsSb, SiC, Ga2O3, BN, and diamond; The substrate is a single crystal substrate, including any one of sapphire, silicon, Ge, SiC, AlN, GaN, GaAs, InP, InAs, GaSb, sapphire / SiO2 composite substrate, Mo, TiW, CuW, Cu, sapphire / AlN composite substrate, diamond, sapphire / SiNx composite substrate, sapphire / SiO2 / SiNx composite substrate, MgAl2O4, MgO, ZnO, ZrB2, LiAlO2 and LiGaO2 composite substrate.

6. A method for preparing a single crystal of a laser having a light absorption loss suppression layer, the laser having a light absorption loss suppression layer according to any one of claims 1 to 5, characterized in that: The single crystal preparation method of the substrate adopts a multi-step method for growth, which specifically includes the following steps: S1: epitaxially grow a seed crystal layer in a MOCVD metal organic chemical vapor epitaxy reaction chamber using a sapphire substrate; S2: placing the seed layer into a HVPE or CVD reaction chamber to grow a single crystal GaN thick film; S3: GaN is peeled off sapphire by stress self-separation or laser lift-off technology to form a GaN single crystal substrate with a defect density of less than or equal to 5E6cm -2 ; S4: transferring the single crystal substrate into a reaction chamber of MOCVD metal organic chemical vapor phase epitaxy, and growing a single crystal of a lower cladding layer by using MOCVD metal organic chemical vapor phase epitaxy; S5: growing a first light absorption loss suppression layer on the lower cladding layer using MOCVD; S6: epitaxially growing a lower waveguide layer, an active layer, and an upper waveguide layer on the first light absorption loss suppression layer by using MOCVD; S7: growing a second light absorption loss suppression layer on the upper waveguide layer using MOCVD; S8: epitaxially growing an upper cladding layer on the second light absorption loss suppression layer using MOCVD.

7. The method for preparing a single crystal of a laser having a light absorption loss suppression layer according to claim 6, characterized in that: In step S1: the seed layer includes a multilayer GaN, the multilayer GaN includes a GaN buffer layer grown at 500-900°C, a pressure of 100-500 Torr, a rotation speed of 600-12000 rpm, and a thickness of 10-200 nm, a GaN three-dimensional growth layer grown at 900-1100°C, a pressure of 150-500 Torr, a rotation speed of 600-12000 rpm, and a thickness of 200-5000 nm, and a GaN two-dimensional growth layer grown at 1000-1200°C, a pressure of 150-250 Torr, a rotation speed of 600-12000 rpm, and a thickness of 2000-10000 nm; In step S2: the temperature is 1000-1200°C, HCl and GaCl3 are introduced into the reaction chamber as gallium sources, NH3 is a nitrogen source, and the thickness is 5-500um; In step S4: the growth temperature is 1000-1200°C, the growth pressure is 100-300 Torr, the reaction elements are TMGa, TEGa, TMAl, TMIn, NH3, N2, H2, the rotation speed is 1000-1300 rpm, the growth rate is 0.2-3 um / h, the V / III ratio is 100-80000, and the doping element is any one of SiH4 or disilane. The lower cladding layer is grown on the substrate by setting the temperature, pressure, reaction element and ratio, rotation speed, growth rate, V / III ratio, and doping element combination; In step S5: the growth temperature is 1000-1150°C, the growth pressure is 100-200 Torr, the reaction elements are TMGa, TEGa, TMAl, TMIn, NH3, N2, H2, the rotation speed is 1000-1300 rpm, the growth rate is 0.5-5um / h, the V / III ratio is 100-80000, and the doping element is any one of SiH4 and disilane. The first light absorption loss suppression layer is grown on the substrate by setting the temperature, pressure, reaction element selection and ratio, rotation speed, growth rate, V / III ratio, and doping element combination; By controlling the Al atom injection curve to y=p x (p>1) The radiation recombination coefficient distribution of the first light absorption loss suppression layer has a function y=x -a (a>1 and is an odd number) the third quadrant curve distribution; By controlling the Al atom injection curve to y=P x (P>1) makes the light absorption coefficient have the function y=d x (d>1) curvilinear distribution; By controlling the Al / Ga element ratio, the curve changes to y=q x (q>1) makes the hole mobility distribution of the first light absorption loss suppression layer have a function y=x -b (b>1 and is an odd number) the third quadrant curve distribution; The Al / Ga element ratio curve is y=Q x (Q>1) density distribution has function y=x -c (c>1 and is an odd number) the third quadrant curve distribution; In step S6: the growth conditions of the lower waveguide layer are as follows: the growth temperature is 650-1000° C., the growth pressure is 100-300 Torr, the reaction elements are TMGa, TEGa, TMAl, TMIn, NH3, N2, H2, the rotation speed is 400-900 rpm, the growth rate is 0.05-2 um / h, the V / III ratio is 1000-90000, and the doping element is any one of SiH4 and disilane. The lower waveguide layer is grown on the substrate by setting the temperature, pressure, reaction element selection and ratio, rotation speed, growth rate, V / III ratio, and doping element combination; The growth conditions of the active layer are as follows: the growth temperature is 600-950°C, the growth pressure is 100-250 Torr, the reaction elements are TEGa, TMAl, TMIn, NH3, N2, H2, the rotation speed is 300-800 revolutions, the growth rate is 0.002-2um / h, the V / III ratio is 1000-90000, and the doping element is any one of SiH4 or disilane. The active layer is grown on the substrate by setting the temperature, pressure, reaction element selection and ratio, rotation speed, growth rate, V / III ratio, and doping element combination; The growth conditions of the upper waveguide layer are as follows: the growth temperature is 650-1000°C, the growth pressure is 100-300 Torr, the reaction elements are TMGa, TEGa, TMAl, TMIn, NH3, N2, H2, the rotation speed is 400-900 revolutions, the growth rate is 0.05-2um / h, the V / III ratio is 1000-90000, and the doping element is any one of SiH4 or disilane. The lower waveguide layer is grown on the substrate by setting the temperature, pressure, reaction element selection and ratio, rotation speed, growth rate, V / III ratio, and doping element combination; In step S7: The growth temperature is 800-1050°C, the growth pressure is 100-200Torr, the reaction elements are TMGa, TEGa, TMAl, TMIn, NH3, N2, H2, the rotation speed is 900-1300 revolutions, the growth rate is 0.5-5um / h, the V / III ratio is 200-80000, and the doping element is any one of SiH4, disilane, or Cp2Mg. The second light absorption loss suppression layer is grown on the substrate by setting the temperature, pressure, reaction element selection and ratio, rotation speed, growth rate, V / III ratio, and doping element combination; By controlling the Al atom implantation curve to be y=j x (0<j<1) curve distribution makes the radiation recombination coefficient distribution of the second light absorption loss suppression layer have a function y=lnx curve distribution; By controlling the Al atom implantation curve to be y=J x The (0<J<1) curve distribution makes the light absorption coefficient distribution of the second light absorption loss suppression layer have a function y=g x (0<g<1) curve distribution; By controlling the Al / Ga element ratio, the curve changes to y=k x (0<k<1) makes the hole mobility distribution of the second light absorption loss suppression layer have a function y=lnx curve distribution; By controlling the Al / Ga element ratio, the curve changes to y=K x (0<K<1) makes the density distribution of the second light absorption loss suppression layer have a function y=lnx curve distribution.

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