Semiconductor laser element with gradient polarization layer

Abstract

The utility model relates to a semiconductor laser element with a gradient polarization layer, which sequentially comprises a substrate, a lower coating layer, a lower wave layer, an active layer, an upper waveguide layer, an electron blocking layer and an upper coating layer from bottom to top, and is characterized in that the gradient polarization layer is arranged between the substrate and the lower coating layer. The piezoelectric polarization coefficient distribution, the spontaneous polarization coefficient distribution, the Philips ionization degree distribution, the elastic coefficient distribution, the covalent bond energy distribution, the polarization optical phonon energy distribution, the transverse sound velocity distribution, the saturated electron drift rate distribution and the like of the gradient polarization layer have special curve distribution; therefore, the semiconductor laser element has the advantages of reducing the polarization effect, reducing the hole migration barrier, reducing the electron leakage and the like.

Description

Technical Field

[0001] The utility model relates to the technical field of semiconductor photoelectric devices, in particular to a semiconductor laser element with a gradient polarization layer. 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, mainly including 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, the spectral half-width is small, the brightness is very high, and the output power of a single laser can be in the W level, while nitride semiconductor light-emitting diodes are spontaneous radiation, and the output power of a single light-emitting diode is in the mW level; 2) The current density of the laser is up to KA / cm 2 , which is more than 2 orders of magnitude higher than that of 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 light; 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: the lattice mismatch and large strain of the active layer induce a strong piezoelectric polarization effect, resulting in a strong QCSE quantum confined Stark effect, causing the energy band of the quantum well to tilt, the step difference of the laser valence band to increase, and the hole injection to be suppressed. The hole transport in the quantum well is more difficult, the carrier injection is uneven, and the probability of electron-hole wave function overlap is reduced, which causes the laser gain to be uneven and the radiation recombination efficiency to decrease, limiting the improvement of the laser's electro-lasing gain. Utility Model Content

[0004] In order to solve the above technical problems, the utility model provides a semiconductor laser element with a gradient polarization layer, which comprises, from bottom to top, a substrate, a lower cladding layer, a lower wave layer, an active layer, an upper waveguide layer, an electron blocking layer, and an upper cladding layer, and is characterized in that a gradient polarization layer is provided between the substrate and the lower cladding layer.

[0005] Specifically, the graded polarization layer is any one or any combination of AlGaN, GaN, AlInN, AlInGaN, InGaN, InGaN / GaN superlattice, InGaN / AlInGaN superlattice, InGaN / AlInN superlattice, AlGaN / AlGaN superlattice, AlGaN / GaN superlattice, AlGaN / AlInGaN superlattice, and AlGaN / AlInN superlattice.

[0006] Specifically, the piezoelectric polarization coefficient distribution, spontaneous polarization coefficient distribution, Philips ionization degree distribution and elastic coefficient distribution of the graded polarization layer have any one of arc distribution, circular arc distribution, curved distribution and irregular curve distribution.

[0007] Specifically, the piezoelectric polarization coefficient distribution of the graded polarization layer has the function y=x -A The third quadrant curve distribution, the spontaneous polarization coefficient distribution of the gradient polarization layer has the function y=x -B The second quadrant curve distribution, the Philips ionization distribution of the gradient polarization layer has the function y=x -C The second quadrant curve distribution, the elastic coefficient distribution of the graded polarization layer has the function y=x -D The second quadrant curve distribution, wherein D>1 and D is an even number, C>1 and C is an even number, B>1 and B is an even number, A>1 and A is an odd number, and D≤C≤A≤B.

[0008] Specifically, the Al element concentration distribution of the graded polarization layer has a function y=x -E The third quadrant curve distribution; the C element concentration distribution of the gradient polarization layer has the function y=x -F The third quadrant curve distribution; the H element concentration distribution of the gradient polarization layer has the function y=x -G The third quadrant curve distribution; the O element concentration distribution of the gradient polarization layer has the function y=x -H The third quadrant curve distribution, wherein H>1 and H is an odd number, G>1 and G is an odd number, F>1 and F is an odd number, E>1 and E is an odd number, and H≤F≤G≤E; the thickness of the graded polarization layer is 30 to 30,000 angstroms.

[0009] Through the above-mentioned technical means, the polarization effect is reduced, the hole migration barrier is lowered, the electron leakage is reduced, the carrier concentration required for the laser lasing to reach the threshold is reduced, the internal loss of the laser and the free carrier absorption loss are reduced, and the temperature stability of the laser and the aging life of the device are improved.

[0010] Specifically, the covalent bond energy distribution, polarization optical phonon energy distribution, transverse sound velocity distribution, and saturated electron drift velocity distribution of the gradient polarization layer have any one of arc distribution, circular arc distribution, curved distribution, and irregular curve distribution.

[0011] Specifically, the covalent bond energy distribution of the graded polarization layer has the function y=x -J The third quadrant curve distribution, the polari-optical phonon energy distribution of the graded polarization layer has the function y=x -K The third quadrant curve distribution, the transverse sound velocity distribution of the graded polarization layer has the function y=x -M The third quadrant curve distribution, the saturated electron drift rate distribution of the gradient polarization layer has the function y=x -N The second quadrant curve distribution, wherein J>1 and J is an odd number, K>1 and K is an odd number, N>1 and N is an even number, M>1 and M is an odd number, and K≤J≤M≤N.

[0012] Through the above-mentioned technical means, carrier diffusion weakens the limiting effect of the abnormal junction barrier on carriers, improves the symmetry of the conduction band and the heavy hole band, and makes the respective quasi-Fermi levels enter their respective energy bands with equal probability under the same injection current, thereby reducing the state density in the valence band and increasing the transition probability to reduce the threshold carrier density, thereby making it easier to meet the particle number inversion conditions and reduce the laser threshold.

[0013] Specifically, the piezoelectric polarization coefficient distribution, spontaneous polarization coefficient distribution, Philips ionization degree distribution, elastic coefficient distribution, covalent bond energy distribution, polarization optical phonon energy distribution, transverse sound velocity distribution, and saturated electron drift rate distribution of the gradient polarization layer have the following relationship: D≤C≤K≤J≤M≤N≤A≤B; the gradient polarization layer can also be located at any position between the lower cladding layer and the lower waveguide layer, between the lower waveguide layer and the active layer, between the active layer and the upper waveguide layer, between the upper waveguide layer and the electron blocking layer, and between the electron blocking layer and the upper cladding layer.

[0014] Specifically, the active layer is a periodic structure composed of a well layer and a barrier layer, the number of periods is 3≥m≥1, the well 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, and the thickness is 10 to 150 angstroms; the barrier layer is GaN, InGaN, InN, AlInN, AlGaN, AlInGaN, AlN, GaAs, GaP, InP, AlGaAs, AlInGaAs, AlGa InP, InGaAs, InGaAsN, AlInAs, AlInP, AlGaP, InGaP, GaSb, InSb, InAs, InAsSb, AlGaSb, AlSb, InGaSb, AlGaAsSb, InGaAsSb, SiC, Ga2O3, BN, and diamond, any one or any combination thereof, with a thickness of 10 to 200 angstroms; the lower cladding layer, the lower waveguide layer, the upper waveguide layer, the electron blocking layer, and the upper cladding layer are GaN, InGaN, InN, AlInN, AlGaN, AlInGaN, AlN, GaAs, GaP, InP, AlGaAs, AlInGaAs, AlGaInP, InGaAs, InGaAsN, AlInAs, AlInP, AlGaP, InGaP, GaSb, InSb, InAs, InAsSb, AlGaSb, Al The invention relates to a substrate comprising any one or any combination of Sb, InGaSb, AlGaAsSb, InGaAsSb, SiC, Ga2O3, BN and diamond; the substrate comprises any one or any combination 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, sapphire / SiO2 / SiNx composite substrate, sapphire / SiNx / SiO2 composite substrate, magnesium aluminum spinel MgAl2O4, MgO, ZnO, ZrB2, LiAlO2 and LiGaO2 composite substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings are included to provide a further understanding of the embodiments and are incorporated into and constitute a part of this specification. The accompanying drawings illustrate the embodiments and are used together with the description to explain the principles of the utility model. It will be easy to recognize other embodiments and many expected advantages of the embodiments because they become better understood by reference to the following detailed description. Other features, objects and advantages of the present application will become more apparent by reading the detailed description of the non-limiting embodiments made with reference to the following drawings:

[0016] Figure 1 is a schematic structural diagram of a semiconductor laser element with a graded polarization layer according to an embodiment of the present application;

[0017] Figure 2 is a SIMS secondary ion mass spectrum of a semiconductor laser element with a graded polarization layer according to an embodiment of the present application;

[0018] Figure 3 This is a SIMS secondary ion mass spectrum (partially enlarged view) of a semiconductor laser element with a graded polarization layer according to an embodiment of the present application;

[0019] Figure 4-8 is a TEM transmission electron microscope image of a semiconductor laser element with a graded polarization layer according to an embodiment of the present application;

[0020] Fig. 9 is a SIMS secondary ion mass spectrum of a semiconductor laser element with a graded polarization layer according to an embodiment of the present application;

[0021] Fig.10 This is a SIMS secondary ion mass spectrum (partially enlarged view) of a semiconductor laser element with a graded polarization layer according to an embodiment of the present application.

[0022] The meaning of the numbers in the figure are: 100, substrate; 101, lower cladding layer; 102, lower waveguide layer; 103, active layer; 104, upper waveguide layer; 105, electron blocking layer; 106, upper cladding layer; 107, graded polarization layer. DETAILED DESCRIPTION

[0023] The present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the relevant utility model, rather than to limit the utility model. It is also necessary to explain that, for ease of description, only the parts related to the utility model are shown in the accompanying drawings.

[0024] like Figure 1As shown, the present application proposes a semiconductor laser element with a graded polarization layer, which includes, from bottom to top, a substrate 100, a lower cladding layer 101, a lower wave layer, an active layer 103, an upper waveguide layer 104, an electron blocking layer 105, and an upper cladding layer 106, characterized in that a graded polarization layer 107 is provided between the substrate 100 and the lower cladding layer 101.

[0025] In order to reduce the polarization effect, lower the hole migration barrier, reduce electron leakage, reduce the carrier concentration required for laser lasing to reach the threshold, reduce the internal loss of the laser and the free carrier absorption loss, and achieve the effect of improving the temperature stability of the laser and the aging life of the device, the piezoelectric polarization coefficient distribution, spontaneous polarization coefficient distribution, Philips ionization degree distribution and elastic coefficient distribution of the gradient polarization layer 107 are specially adjusted so that the piezoelectric polarization coefficient distribution, spontaneous polarization coefficient distribution, Philips ionization degree distribution and elastic coefficient distribution have any one of arc distribution, circular arc distribution, curved distribution and irregular curve distribution.

[0026] Specifically, the piezoelectric polarization coefficient distribution of the graded polarization layer has the function y=x -A The third quadrant curve distribution, where A>1 and A is an odd number;

[0027] Specifically, the spontaneous polarization coefficient distribution of the graded polarization layer has the function y=x -B The second quadrant curve distribution, where B>1 and B is an even number;

[0028] Specifically, the Philips ionization distribution of the graded polarization layer has the function y=x -C The second quadrant curve distribution, where C>1 and C is an even number;

[0029] Specifically, the elastic coefficient distribution of the graded polarization layer has the function y=x -D The second quadrant curve distribution, where D>1 and D is an even number;

[0030] In the first specific embodiment, the piezoelectric polarization coefficient distribution, spontaneous polarization coefficient distribution, Philips ionization degree distribution and elastic coefficient distribution of the graded polarization layer 107 can be adjusted simultaneously so that when it satisfies the above curve distribution, it also satisfies D≤C≤A≤B, thereby better achieving the technical effect.

[0031] In order to make carrier diffusion weaken the restrictive effect of abnormal junction barrier on carriers, thereby improving the symmetry of conduction band and heavy hole band, so that the respective quasi-Fermi levels will enter their respective energy bands with equal probability under the same injection current, reduce the state density in the valence band and increase the transition probability to reduce the threshold carrier density, thereby easily satisfying the particle number inversion condition and reducing the technical effect of the laser threshold; the present application makes special adjustments to the covalent bond energy distribution, polarization optical phonon energy distribution, transverse sound velocity distribution, and saturated electron drift rate distribution of the gradient polarization layer, so that the above distribution has any one of arc distribution, circular arc distribution, curved distribution, and irregular curve distribution.

[0032] Specifically, the covalent bond energy distribution of the graded polarization layer has the function y=x -J The third quadrant curve distribution, where J>1 and J is an odd number;

[0033] Specifically, the polari-optical phonon energy distribution of the graded polarimetric layer has the function y=x -K The third quadrant curve distribution, where K>1 and K is an odd number;

[0034] Specifically, the saturated electron drift velocity distribution of the graded polarization layer has the function y=x -N The second quadrant curve distribution, where N>1 and N is an even number;

[0035] Specifically, the transverse sound velocity distribution of the graded polarization layer has the function y=x -M The third quadrant curve distribution, where M>1 and M is an odd number;

[0036] In the second specific embodiment, the covalent bond energy distribution, polarization optical phonon energy distribution, transverse sound velocity distribution, and saturated electron drift rate distribution of the gradient polarization layer 107 can be adjusted simultaneously so that when they satisfy the above curve distribution, they also satisfy K≤J≤M≤N, thereby better achieving the technical effect.

[0037] In the third specific embodiment, in order to simultaneously achieve the effects of the first specific embodiment and the second specific embodiment, the piezoelectric polarization coefficient distribution, spontaneous polarization coefficient distribution, Philips ionization degree distribution, elastic coefficient distribution, covalent bond energy distribution, polarization optical phonon energy distribution, transverse sound velocity distribution, and saturated electron drift rate distribution of the gradient polarization layer 107 can be adjusted simultaneously so that the above distributions have the following relationship: D≤C≤K≤J≤M≤N≤A≤B.

[0038] Specifically, the Al element concentration distribution of the graded polarization layer 107 has a function y=x -E The third quadrant curve distribution; the C element concentration distribution of the gradient polarization layer has the function y=x -F The third quadrant curve distribution; the H element concentration distribution of the gradient polarization layer has the function y=x-G The third quadrant curve distribution; the O element concentration distribution of the gradient polarization layer has the function y=x -H The third quadrant curve distribution, wherein H>1 and H is an odd number, G>1 and G is an odd number, F>1 and F is an odd number, E>1 and E is an odd number, and H≤F≤G≤E.

[0039] In a specific embodiment, Figure 2 and Figure 3 As shown, the Al element concentration of the graded polarization layer 107 gradually decreases from the lower cladding layer 101 to the substrate 100, and the decreasing curve has a function y=x -E The third quadrant curve distribution;

[0040] In a specific embodiment, Fig. 9 and Fig.10 As shown, the Al concentration of the variable polarization layer 107 gradually decreases from the lower cladding layer 101 to the substrate 100, and the decreasing curve has a function y=x -E The third quadrant curve distribution; the C element concentration distribution of the graded polarization layer 107 has a function y=x -F The third quadrant curve distribution, O element concentration distribution has the function y=x -H The curve distribution in the third quadrant is as follows: the concentrations of C and O in the graded polarization layer 107 are close to each other; the concentration distribution of H in the graded polarization layer 107 has a function y=x -G The curve is distributed in the third quadrant, and the H element concentration in the graded polarization layer 107 is between the Al element concentration and the C and O element concentrations.

[0041] At the same time, the above technical solutions can achieve the following effects:

[0042]

[0043] Specifically, in order to better regulate the piezoelectric polarization coefficient distribution, spontaneous polarization coefficient distribution, Philips ionization degree distribution, elastic coefficient distribution, covalent bond energy distribution, polarization optical phonon energy distribution, transverse sound velocity distribution, and saturated electron drift rate distribution of the graded polarization layer 107 to have the above-mentioned curve distribution, the graded polarization layer 107 is usually AlGaN, GaN, AlInN, AlInGaN, InGaN, InGaN / GaN superlattice, InGaN / AlInGaN superlattice, InGaN / AlInN superlattice, AlGaN / AlGaN superlattice, AlGaN / GaN superlattice, AlGaN / AlInGaN superlattice, AlGaN / AlInGaN superlattice, AlGaN / AlInGaN superlattice, AlGaN / AlInGaN superlattice, Any one or any combination of InN superlattices, and the thickness of the graded polarization layer 107 is 30 to 30,000 angstroms; the graded polarization layer can also be located at any position between the lower cladding layer and the lower waveguide layer, between the lower waveguide layer and the active layer, between the active layer and the upper waveguide layer, between the upper waveguide layer and the electron blocking layer, and between the electron blocking layer and the upper cladding layer.

[0044] Specifically, the active layer 103 is a periodic structure composed of a well layer and a barrier layer, the period number is 3≥m≥1, the well 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, and the thickness is 10 to 150 angstroms, and the barrier layer is GaN, InGaN, InN, AlInN, AlGaN, AlInGaN, AlN, GaAs, GaP, InP, AlGaAs, AlIn 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, InGaAsSb, SiC, Ga2O3, BN, and diamond, with a thickness of 10 to 200 angstroms; the lower cladding layer 101, the lower waveguide layer 102, the upper waveguide layer 104, the electron blocking layer 105, and the upper cladding layer 106 are GaN, InGaN, InN, AlInN, AlGaN, AlInGaN, AlN, GaAs, GaP, InP, AlGaAs, AlInGaAs, AlGaInP, InGaAs, InGaAsN, AlInAs, AlInP, AlGaP, I Any one or any combination of nGaP, GaSb, InSb, InAs, InAsSb, AlGaSb, AlSb, InGaSb, AlGaAsSb, InGaAsSb, SiC, Ga2O3, BN, and diamond;The substrate 100 includes 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, sapphire / SiO2 / SiNx composite substrate, sapphire / SiNx / SiO2 composite substrate, magnesium aluminum spinel MgAl2O4, MgO, ZnO, ZrB2, LiAlO2 and LiGaO2 composite substrate. ;

[0045] like Figure 4 As shown, the thickness of the upper cladding layer 106 in this embodiment is 2827 angstroms.

[0046] like Figure 5 As shown, in this embodiment, the electron blocking layer 105 is composed of multiple components, and the thicknesses of different components include: 16 angstroms, 19 angstroms, 21 angstroms, 23 angstroms, 25 angstroms, 31 angstroms, 36 angstroms and 37 angstroms, and there is also a transition region with a thickness of 116 angstroms in the transition region from the electron blocking layer 105 to the upper waveguide layer 104, and the composition of this region is different from that of other regions.

[0047] like Figure 6 As shown, in this embodiment, the thickness of the upper waveguide layer 104 is 2471 angstroms.

[0048] like Figure 7 As shown, in this embodiment, by observing the TEM image at a scale of 10 nm, it can be seen that the active layer is a periodic structure composed of a well layer and a barrier layer, and the number of periods is between 1 and 3.

[0049] like Figure 8 As shown, in this embodiment, the thickness of the lower waveguide layer 102 is 5387 angstroms.

[0050] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the utility model. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

Claims

1. A semiconductor laser element with a graded polarization layer, comprising, from bottom to top, a substrate, a lower cladding layer, a lower wave layer, an active layer, an upper waveguide layer, an electron blocking layer, and an upper cladding layer, characterized in that: A graded polarization layer is provided between the substrate and the lower cladding layer.

2. A semiconductor laser element with a graded polarization layer as claimed in claim 1, characterized in that: The piezoelectric polarization coefficient distribution, spontaneous polarization coefficient distribution, Philips ionization degree distribution and elastic coefficient distribution of the graded polarization layer have any one of arc distribution, circular arc distribution, curved distribution and irregular curve distribution.

3. A semiconductor laser element with a graded polarization layer as claimed in claim 2, characterized in that: The piezoelectric polarization coefficient distribution of the graded polarization layer has a function y=x -A The third quadrant curve distribution, the spontaneous polarization coefficient distribution of the graded polarization layer has a function y=x -B The second quadrant curve distribution, the Philips ionization degree distribution of the graded polarization layer has a function y=x -C The second quadrant curve distribution, the elastic coefficient distribution of the graded polarization layer has a function y=x -D The second quadrant curve distribution, wherein D>1 and D is an even number, C>1 and C is an even number, B>1 and B is an even number, A>1 and A is an odd number, and D≤C≤A≤B.

4. A semiconductor laser element with a graded polarization layer as claimed in claim 3, characterized in that: The Al element concentration distribution of the graded polarization layer has a function y=x -E The third quadrant curve distribution; the C element concentration distribution of the gradient polarization layer has a function y=x -F The third quadrant curve distribution; the H element concentration distribution of the gradient polarization layer has a function y=x -G The third quadrant curve distribution; the O element concentration distribution of the gradient polarization layer has a function y=x -H The third quadrant curve distribution, wherein H>1 and H is an odd number, G>1 and G is an odd number, F>1 and F is an odd number, E>1 and E is an odd number, and H≤F≤G≤E; the thickness of the graded polarization layer is 30 to 30,000 angstroms.

5. A semiconductor laser element with a graded polarization layer as claimed in claim 3, characterized in that: The covalent bond energy distribution, polarization optical phonon energy distribution, transverse sound velocity distribution, and saturated electron drift velocity distribution of the gradient polarization layer have any one of arc distribution, circular arc distribution, curved distribution, and irregular curve distribution.

6. A semiconductor laser element with a graded polarization layer as claimed in claim 5, characterized in that: The covalent bond energy distribution of the graded polarization layer has a function y=x -J The third quadrant curve distribution, the polarization optical phonon energy distribution of the graded polarization layer has a function y=x -K The third quadrant curve distribution, the transverse sound velocity distribution of the graded polarization layer has a function y=x -M The third quadrant curve distribution, the saturated electron drift rate distribution of the graded polarization layer has a function y=x -N The second quadrant curve distribution, wherein J>1 and J is an odd number, K>1 and K is an odd number, N>1 and N is an even number, M>1 and M is an odd number, and K≤J≤M≤N.

7. A semiconductor laser element with a graded polarization layer as claimed in claim 6, characterized in that: The piezoelectric polarization coefficient distribution, spontaneous polarization coefficient distribution, Philips ionization degree distribution, elastic coefficient distribution, covalent bond energy distribution, polarization optical phonon energy distribution, transverse sound velocity distribution, and saturated electron drift rate distribution of the gradient polarization layer have the following relationship: D≤C≤K≤J≤M≤N≤A≤B; the gradient polarization layer can also be located at any position between the lower cladding layer and the lower waveguide layer, between the lower waveguide layer and the active layer, between the active layer and the upper waveguide layer, between the upper waveguide layer and the electron blocking layer, and between the electron blocking layer and the upper cladding layer.

8. A semiconductor laser element with a graded polarization layer as claimed in claim 1, characterized in that: The active layer is a periodic structure composed of a well layer and a barrier layer, the period number is 3≥m≥1, the thickness is 10-150 angstroms, and the thickness of the barrier layer is 10-200 angstroms.

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