Group III nitride semiconductor laser element

Abstract

The invention discloses a group III nitride semiconductor laser element which sequentially comprises a substrate, a lower limiting layer, a lower waveguide layer, an active layer, an upper waveguide layer and an upper limiting layer from bottom to top. The Fermi noodle topological layer comprises a first Fermi noodle topological layer, a second Fermi noodle topological layer and a third Fermi noodle topological layer. According to the invention, through specific design of conduction band effective state density distribution and thermal conductivity distribution, vertically downward energy band movement is formed to change a Fermi surface topological structure, disorder and instability of electron spinning are reduced, state density in a valence band is reduced, and transition probability is increased to reduce threshold current density, hole migration barrier and electron leakage; the electron hole confinement effect of the active layer is improved, and the stimulated radiation recombination efficiency is enhanced, so that the optical power and the slope efficiency are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor optoelectronic devices, and in particular to a group-III nitride semiconductor laser element. Background Art

[0002] Lasers are widely used in the fields of laser display, laser TV, laser projector, communication, medical treatment, weapon, guidance, ranging, spectral analysis, cutting, precision welding, high-density optical storage, etc. There are many types of lasers, and the classification methods are also diverse. Mainly there are solid-state, gas, liquid, semiconductor, dye and other types of lasers; compared with other types of lasers, all-solid-state semiconductor lasers have the advantages of small volume, high efficiency, light weight, good stability, long life, simple and compact structure, miniaturization, etc.

[0003] There are great differences between lasers and nitride semiconductor light-emitting diodes. 1) Laser is generated by stimulated emission of carriers, with a relatively small spectral full width at half maximum, very high brightness, and the output power of a single laser can be in the watt level, while nitride semiconductor light-emitting diodes are spontaneous emission, and the output power of a single light-emitting diode is in the milliwatt level; 2) The operating current density of lasers reaches KA / cm 2 which is more than two orders of magnitude higher than that of nitride light-emitting diodes, thus causing stronger electron leakage, more serious Auger recombination, stronger polarization effect, more serious electron-hole mismatch, resulting in more serious efficiency droop effect; 3) Light-emitting diodes are spontaneous transition radiation, without external action, incoherent light that transitions from a high energy level to a low energy level, while lasers are stimulated transition radiation, and the induced photon energy should be equal to the energy difference between the electron transitions, generating completely identical coherent light of photons and induced photons; 4) Different principles: Light-emitting diodes are under the action of an external voltage, and electrons and holes transition to quantum wells or p-n junctions to generate radiative recombination light, while lasers need to meet the lasing conditions to lase. It must satisfy the carrier population inversion distribution in the active region, and the stimulated emission light oscillates back and forth in the resonant cavity. The propagation in the gain medium amplifies the light, satisfies the threshold condition that the gain is greater than the loss, and finally outputs laser light.

[0004] Nitride semiconductor lasers have the following problems: 1) The Mg acceptor activation energy of p-type semiconductors is large, the ionization efficiency is low, the hole concentration is much lower than the electron concentration, and the hole mobility is much smaller than the electron mobility. The electrons and holes in the active layer are seriously asymmetric and mismatched, resulting in problems such as low hole injection efficiency and electron overflow, reducing the electron-hole radiative recombination efficiency in the active layer. 2) After the laser lases, the carrier concentration in the multi-quantum well active region is saturated, the bipolar conductivity effect weakens, and the series resistance of the laser increases, resulting in an increase in the laser voltage. Summary of the Invention

[0005] The present invention provides a group-III nitride semiconductor laser device, which forms a vertically downward energy band shift to change the Fermi surface topology by a specifically designed conduction band effective density of states distribution and thermal conductivity distribution, reduces the disorder and instability of electron spins, reduces the density of states in the valence band and increases the transition probability to reduce the threshold current density, reduces the hole migration barrier, reduces electron leakage, enhances the electron-hole confinement effect in the active layer, and enhances the stimulated emission recombination efficiency, thereby improving the optical power and slope efficiency.

[0006] A group-III nitride semiconductor laser device provided by the present invention sequentially includes a substrate, a lower confinement layer, a lower waveguide layer, an active layer, an upper waveguide layer, and an upper confinement layer from bottom to top. A Fermi surface topology layer is disposed above the upper confinement layer, and the Fermi surface topology layer includes a first Fermi surface topology layer, a second Fermi surface topology layer, and a third Fermi surface topology layer.

[0007] Preferably, the conduction band effective density of states distribution of the first Fermi surface topology layer has a curve distribution of the function y = A + B*lnx - C*x + 1; the conduction band effective density of states distribution of the second Fermi surface topology layer has a linear function curve distribution; the conduction band effective density of states distribution of the third Fermi surface topology layer has a curve distribution of the function y = D + E*x / e x curve distribution; the conduction band effective density of states of the first Fermi surface topology layer is d, the conduction band effective density of states of the second Fermi surface topology layer is e, and the conduction band effective density of states of the third Fermi surface topology layer is f, where: 1E17 ≤ f ≤ e ≤ d ≤ 5E19 (cm -3 )

[0008] Preferably, the thermal conductivity distribution of the first Fermi surface topology layer has a curve distribution of the function y = F + G*lnx - H*e x curve distribution; the thermal conductivity distribution of the second Fermi surface topology layer has a linear function curve distribution; the thermal conductivity distribution of the third Fermi surface topology layer has a curve distribution of the function y = I + J*lnx / e x curve distribution; the thermal conductivity of the first Fermi surface topology layer is g, the thermal conductivity of the second Fermi surface topology layer is h, and the thermal conductivity of the third Fermi surface topology layer is i, where: 0.1 ≤ i ≤ h ≤ g ≤ 15 (W / cm -1 s)

[0009] Preferably, the refractive index coefficient distribution of the first Fermi surface topology layer has a curve distribution of the function y = K + L*x + 1 / 2x in the first quadrant; the refractive index coefficient distribution of the second Fermi surface topology layer has a linear function curve distribution; the refractive index coefficient distribution of the third Fermi surface topology layer has a function y = M + N*(e x +e -x ) / (e x -e -x)First quadrant curve distribution; the refractive index coefficient of the first Fermi surface topological layer is j, the refractive index coefficient of the second Fermi surface topological layer is k, and the refractive index coefficient of the third Fermi surface topological layer is l, where: 1.0 ≤ j ≤ k ≤ l ≤ 10.

[0010] Preferably, the electron effective mass distribution of the first Fermi surface topological layer has a function y = O + P * ln(x + 1) - Q * e x Curve distribution; the electron effective mass distribution of the second Fermi surface topological layer has a linear function curve distribution; the electron effective mass distribution of the third Fermi surface topological layer has a function y = R + S * lnx / x curve distribution; the electron effective mass of the first Fermi surface topological layer is m, the electron effective mass of the second Fermi surface topological layer is n, and the electron effective mass of the third Fermi surface topological layer is p, where: 0.01 ≤ p ≤ n ≤ m ≤ 5.

[0011] Preferably, the Fermi surface topological 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, diamond.

[0012] Preferably, the active layer is a periodic structure composed of well layers and barrier layers, the number of periods is 3 ≥ m ≥ 1, the well layer is any one or any combination of InGaN, InN, AlInN, GaN, with a thickness of 10 - 80 angstroms, and the barrier layer is any one or any combination of GaN, AlGaN, AlInGaN, AlN, AlInN, with a thickness of 10 - 120 angstroms.

[0013] Preferably, the lower confinement layer, lower waveguide layer, upper waveguide layer, and upper confinement 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, diamond.

[0014] Preferably, the substrate includes any one of sapphire, silicon, Ge, SiC, AlN, Cu, Mo, TiW, W, CuW, GaN, GaAs, InP, InAs, GaSb, diamond, sapphire / SiO2 composite substrate, sapphire / AlN composite substrate, sapphire / SiN x , sapphire / SiO2 / SiN x composite substrate, magnesium aluminate spinel MgAl2O4, MgO, ZnO, ZrB2, LiAlO2, and LiGaO2 composite substrate.

[0015] Compared with the prior art, the beneficial effects of a group III nitride semiconductor laser element provided by an embodiment of the present invention are as follows: The Fermi surface topology layer forms a vertically downward energy band shift by a specifically designed conduction band effective state density distribution and thermal conductivity distribution to change the Fermi surface topology structure, reduce the disorder and instability of electron spin, reduce the state density in the valence band and increase the transition probability to reduce the threshold current density, reduce the hole migration barrier, reduce electron leakage, enhance the electron-hole confinement effect of the active layer, and enhance the stimulated emission recombination efficiency, thereby improving the optical power and slope efficiency. The Fermi surface topology layer can enhance bipolar conductance by a specifically designed refractive index coefficient distribution and electron effective mass distribution to improve the confinement factor and improve the problem of carrier concentration saturation in the active layer, thereby reducing the excitation threshold of the laser element and improving the optical power and slope efficiency of the laser element. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 FIG. is a schematic structural diagram of a group III nitride semiconductor laser element provided by the present invention.

[0017] Figure 2 FIG. is a SIMS secondary ion mass spectrum of a group III nitride semiconductor laser element provided by the present invention.

[0018] In the figure: 100: substrate; 101: lower confinement layer; 102: lower waveguide layer; 103: active layer; 104: upper waveguide layer; 105: upper confinement layer; 106: Fermi surface topology layer; 106a: first Fermi surface topology layer; 106b: second Fermi surface topology layer; 106c: third Fermi surface topology layer. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0020] To solve the above problems, a III-nitride semiconductor laser element provided by an embodiment of the present application will be introduced and described in detail through the following specific embodiments.

[0021] Referring to Figure 1-2 , a III-nitride semiconductor laser element provided by the present invention sequentially includes a substrate 100, a lower confinement layer 101, a lower waveguide layer 102, an active layer 103, an upper waveguide layer 104, and an upper confinement layer 105 from bottom to top. A Fermi surface topology layer 106 is disposed above the upper confinement layer 105. The Fermi surface topology layer 106 includes a first Fermi surface topology layer 106a, a second Fermi surface topology layer 106b, and a third Fermi surface topology layer 106c.

[0022] Among them, the Fermi surface topology layer 106 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.

[0023] The conduction band effective density of states distribution of the first Fermi surface topology layer 106a has a curve distribution of the function y = A + B*lnx - C*x + 1; the conduction band effective density of states distribution of the second Fermi surface topology layer 106b has a linear function curve distribution; the conduction band effective density of states distribution of the third Fermi surface topology layer 106c has a curve distribution of the function y = D + E*x / e x ; the conduction band effective density of states of the first Fermi surface topology layer 106a is d, the conduction band effective density of states of the second Fermi surface topology layer 106b is e, and the conduction band effective density of states of the third Fermi surface topology layer 106c is f, where: 1E17 ≤ f ≤ e ≤ d ≤ 5E19 (cm -3 ).

[0024] The thermal conductivity distribution of the first Fermi surface topology layer 106a has a curve distribution of the function y = F + G*lnx - H*e x ; the thermal conductivity distribution of the second Fermi surface topology layer 106b has a linear function curve distribution; the thermal conductivity distribution of the third Fermi surface topology layer 106c has a curve distribution of the function y = I + J*lnx / e xCurve distribution; the thermal conductivity of the first Fermi surface topological layer 106a is g, the thermal conductivity of the second Fermi surface topological layer 106b is h, and the thermal conductivity of the third Fermi surface topological layer 106c is i, where: 0.1 ≤ i ≤ h ≤ g ≤ 15 (W / cm -1 s).

[0025] As can be seen from the above, the Fermi surface topological layer forms a vertically downward energy band shift through the conduction band effective state density distribution and thermal conductivity distribution with specific designs to change the Fermi surface topological structure, reduce the disorder and instability of electron spin, reduce the state density in the valence band and increase the transition probability to reduce the threshold current density, reduce the hole migration barrier, reduce electron leakage, enhance the electron-hole confinement effect of the active layer, and enhance the stimulated emission recombination efficiency, thereby improving the optical power and slope efficiency.

[0026] The refractive index coefficient distribution of the first Fermi surface topological layer 106a has a curve distribution of the function y = K + L*x + 1 / 2x in the first quadrant; the refractive index coefficient distribution of the second Fermi surface topological layer 106b has a linear function curve distribution; the refractive index coefficient distribution of the third Fermi surface topological layer 106c has a curve distribution of the function y = M + N*e x +e -x / (e x -e -x ) in the first quadrant; the refractive index coefficient of the first Fermi surface topological layer 106a is j, the refractive index coefficient of the second Fermi surface topological layer 106b is k, and the refractive index coefficient of the third Fermi surface topological layer 106c is l, where: 1.0 ≤ j ≤ k ≤ l ≤ 10.

[0027] The electron effective mass distribution of the first Fermi surface topological layer 106a has a curve distribution of the function y = O + P*ln(x + 1) - Q*e x ; the electron effective mass distribution of the second Fermi surface topological layer 106b has a linear function curve distribution; the electron effective mass distribution of the third Fermi surface topological layer 106c has a curve distribution of the function y = R + S*lnx / x; the electron effective mass of the first Fermi surface topological layer 106a is m, the electron effective mass of the second Fermi surface topological layer 106b is n, and the electron effective mass of the third Fermi surface topological layer 106c is p, where: 0.01 ≤ p ≤ n ≤ m ≤ 5.

[0028] As can be seen from the above, the Fermi surface topological layer can enhance the bipolar conductivity through the refractive index coefficient distribution and electron effective mass distribution with specific designs to improve the confinement factor and solve the problem of carrier concentration saturation in the active layer, thereby reducing the excitation threshold of the laser element and improving the optical power and slope efficiency of the laser element.

[0029] Specifically as shown in the following table, specific data comparisons of the traditional laser and the laser of the present invention are made in four aspects: limiting factor, oblique light efficiency, threshold current density, and optical power.

[0030] Blue Laser - Project Conventional Laser Laser of the Present Invention Variation Range Limiting Factor 1.40％ 3.29％ 135％ Slope Efficiency (W / A) 0.8 1.79 124％ <![CDATA[Threshold current density (kA / cm 2 )]]> 2.4 0.73 -70％ Optical Power (W) 4.1 13.1 220％

[0031] In the present invention, the active layer 103 is a periodic structure composed of well layers and barrier layers, where the number of periods m satisfies 3≥m≥1. The well layer is any one or any combination of InGaN, InN, AlInN, and GaN, with a thickness of 10 to 80 angstroms, and the barrier layer is any one or any combination of GaN, AlGaN, AlInGaN, AlN, and AlInN, with a thickness of 10 to 120 angstroms.

[0032] In the present invention, the lower confinement layer 101, the lower waveguide layer 102, the upper waveguide layer 104, and the upper confinement 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.

[0033] In the present invention, the substrate 100 includes sapphire, silicon, Ge, SiC, AlN, Cu, Mo, TiW, W, CuW, GaN, GaAs, InP, InAs, GaSb, diamond, sapphire / SiO2 composite substrate, sapphire / AlN composite substrate, sapphire / SiN x , sapphire / SiO2 / SiN x composite substrate, magnesium aluminate spinel MgAl2O4, MgO, ZnO, ZrB2, LiAlO2 and LiGaO2 composite substrate, any one of them.

[0034] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and deformations can be made, and these improvements and deformations should also be regarded as the protection scope of the present invention.

Claims

1. A group-III nitride semiconductor laser device, which sequentially includes a substrate (100), a lower confinement layer (101), a lower waveguide layer (102), an active layer (103), an upper waveguide layer (104), and an upper confinement layer (105) from bottom to top, and is characterized in that, Above the upper confinement layer (105) there is a Fermi surface topological layer (106), and the Fermi surface topological layer (106) includes a first Fermi surface topological layer (106a), a second Fermi surface topological layer (106b), and a third Fermi surface topological layer (106c).

2. The group-III nitride semiconductor laser element according to claim 1, characterized in that, The conduction band effective density of states distribution of the first Fermi surface topological layer (106a) has a curve distribution of the function y = A + B*lnx - C*x + 1; the conduction band effective density of states distribution of the second Fermi surface topological layer (106b) has a linear function curve distribution; the conduction band effective density of states distribution of the third Fermi surface topological layer (106c) has a curve distribution of the function y = D + E*x / e x ; the conduction band effective density of states of the first Fermi surface topological layer (106a) is d, the conduction band effective density of states of the second Fermi surface topological layer (106b) is e, and the conduction band effective density of states of the third Fermi surface topological layer (106c) is f, where: 1E17 ≤ f ≤ e ≤ d ≤ 5E19 (cm -3 ).

3. The nitride semiconductor laser element according to claim 1, wherein The thermal conductivity distribution of the first Fermi surface topological layer (106a) has a function curve distribution of y = F + G*lnx - H*e x ; the thermal conductivity distribution of the second Fermi surface topological layer (106b) has a linear function curve distribution; the thermal conductivity distribution of the third Fermi surface topological layer (106c) has a function curve distribution of y = I + J*lnx / e x ; the thermal conductivity of the first Fermi surface topological layer (106a) is g, the thermal conductivity of the second Fermi surface topological layer (106b) is h, and the thermal conductivity of the third Fermi surface topological layer (106c) is i, where: 0.1 ≤ i ≤ h ≤ g ≤ 15 (W / cm -1 s).

4. The III-nitride semiconductor laser element according to claim 1, wherein The refractive index coefficient distribution of the first Fermi surface topological layer (106a) has a curve distribution of the function y = K + L * x + 1 / 2x in the first quadrant; the refractive index coefficient distribution of the second Fermi surface topological layer (106b) has a linear function curve distribution; the refractive index coefficient distribution of the third Fermi surface topological layer (106c) has a curve distribution of the function y = M + N * (e x + e -x ) / (e x - e -x ) in the first quadrant; the refractive index coefficient of the first Fermi surface topological layer (106a) is j, the refractive index coefficient of the second Fermi surface topological layer (106b) is k, and the refractive index coefficient of the third Fermi surface topological layer (106c) is l, where: 1.0 ≤ j ≤ k ≤ l ≤ 10.

5. The nitride semiconductor laser element according to claim 1, characterized in that The electron effective mass distribution of the first Fermi surface topological layer (106a) has a functional curve distribution of y = O + P * ln(x + 1) - Q * e x curve distribution; the electron effective mass distribution of the second Fermi surface topological layer (106b) has a linear functional curve distribution; the electron effective mass distribution of the third Fermi surface topological layer (106c) has a functional curve distribution of y = R + S * lnx / x; the electron effective mass of the first Fermi surface topological layer (106a) is m, the electron effective mass of the second Fermi surface topological layer (106b) is n, and the electron effective mass of the third Fermi surface topological layer (106c) is p, where: 0.01 ≤ p ≤ n ≤ m ≤ 5.

6. The nitride semiconductor laser element according to claim 1, characterized in that, The Fermi surface topological layer (106) 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.

7. The group-III nitride semiconductor laser element according to claim 1, wherein The active layer (103) is a periodic structure composed of well layers and barrier layers, where the number of periods satisfies 3≥m≥1. The well layers are any one or any combination of InGaN, InN, AlInN, and GaN, with a thickness of 10 to 80 angstroms, and the barrier layers are any one or any combination of GaN, AlGaN, AlInGaN, AlN, and AlInN, with a thickness of 10 to 120 angstroms.

8. The nitride semiconductor laser element according to claim 1, wherein The lower confinement layer (101), the lower waveguide layer (102), the upper waveguide layer (104), and the upper confinement 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.

9. The nitride semiconductor laser device according to claim 1, wherein The substrate (100) includes any one of sapphire, silicon, Ge, SiC, AlN, Cu, Mo, TiW, W, CuW, GaN, GaAs, InP, InAs, GaSb, diamond, sapphire / SiO2 composite substrate, sapphire / AlN composite substrate, sapphire / SiN x , sapphire / SiO2 / SiN x composite substrate, magnesium aluminate spinel MgAl2O4, MgO, ZnO, ZrB2, LiAlO2, and LiGaO2 composite substrate.

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