Nitride semiconductor laser element

Abstract

The invention discloses a 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, and a self-bound exciton polariton layer is arranged between the lower waveguide layer and the lower limiting layer. The self-bound exciton polariton layer comprises a first self-bound exciton polariton layer and a second self-bound exciton polariton layer. According to the invention, a topological monoclinic phase periodic ferroelectric domain is provided, strong out-of-plane spontaneous polarization is formed to induce self-bound exciton polaritons, free exciton bound energy is increased from less than 10 meV to more than 20 meV, a temperature threshold of laser exciton radiation is reduced, and exciton optical radiation can be realized at room temperature or higher temperature.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor optoelectronic devices, and in particular to a nitride semiconductor laser element. 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.

[0003] There are big differences between lasers and nitride semiconductor light-emitting diodes. 1) When light resonates with the two-level atoms of the gain medium, there are three processes: absorption, spontaneous radiation, and stimulated radiation. The phase of spontaneous radiation is chaotic and irregular, and the spontaneous transition is random. The spontaneous radiation that deviates from the axis escapes from the cavity. Photons with specific frequencies, specific directions, and lateral distributions along the axis cause avalanche-like stimulated amplification to produce lasers. Lasers are generated by stimulated radiation of carriers. It must satisfy the conditions that stimulated radiation is greater than absorption, and that the number of particles is inverted, and the gain is greater than the loss, so as to achieve light amplification. The laser spectrum has a small half-width, good monochromaticity and directionality, and high brightness. The output power of a single laser can be in the W level, while nitride semiconductor light-emitting diodes emit spontaneous radiation, which does not require the number of particles to be inverted and the stimulated radiation is greater than the absorption condition. The light-emitting diode spectrum has a large half-width and is not monochromatic. The output power of a single light-emitting diode is in the mW level. 2) The current density of the laser is 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) The light-emitting diode spontaneously radiates, without external influence, and is incoherent light that transitions from high energy level to low energy level, while the laser is stimulated transition radiation, and the energy of the induced photon should be equal to the difference in energy levels of the electron transition, generating photons and induced photons. The photons and induced photons are completely coherent light with strong high coherence; 4) The principles are different: the light-emitting diode is under the action of external voltage, and the electron hole transitions to the quantum well or pn junction to produce radiation recombination and light emission, while the laser needs the lasing conditions to be met before it can be lased. The carrier inversion distribution in the active area must be met, and the stimulated radiation light oscillates back and forth in the resonant cavity. The propagation in the gain medium amplifies the light, and the threshold condition is met so that the gain is greater than the loss, and finally the laser is output.

[0004] Nitride semiconductor lasers have the following problems: 1) The large internal lattice mismatch and strain cause strong polarization effects, and the QCSE quantum confinement Stark effect strongly limits the improvement of the laser's electro-lasing gain; 2) The Mg acceptor activation energy of the p-type semiconductor is large, the ionization efficiency is low, the hole concentration is much lower than the electron concentration, and the hole mobility is much lower than the electron mobility, resulting in serious asymmetric mismatch between electrons and holes in the quantum well, electron leakage and carrier delocalization, more difficult hole transport in the quantum well, uneven carrier injection, uneven gain, and a widened laser gain spectrum with a decreased peak gain. 3) The laser valence band step difference increases, making it more difficult for holes to transport in the quantum well, uneven carrier injection, and uneven gain. Summary of the invention

[0005] The present invention proposes a nitride semiconductor laser element, wherein the self-bound exciton polariton layer has a topological monoclinic periodic ferroelectric domain, forms a strong out-of-plane spontaneous polarization-induced self-bound exciton polariton, increases the free exciton binding energy from below 10 meV to above 20 meV, reduces the temperature threshold of the laser's exciton radiation, and can achieve exciton light radiation at room temperature or higher.

[0006] A nitride semiconductor laser element provided by the present invention comprises, from bottom to top, a substrate, a lower confinement layer, a lower waveguide layer, an active layer, an upper waveguide layer, and an upper confinement layer, wherein a self-bound exciton polariton layer is provided between the lower waveguide layer and the lower confinement layer, wherein the self-bound exciton polariton layer comprises a first self-bound exciton polariton layer and a second self-bound exciton polariton layer; the self-bound exciton polariton layer is GaN, InGaN, InN, AlInN, AlGaN, AlInGaN, AlN, InGaN / GaN superlattice, InGaN / AlGaN superlattice, InGaN / AlInGaN superlattice, InG Any one or any combination of aN / AlInN superlattice, GaN / AlGaN superlattice, GaN / AlInGaN superlattice, GaN / AlN superlattice, GaAs, GaP, InP, AlGaAs, AlInGaAs, AlGaInP, InGaAs, InGaAsN, AlInAs, AlInP, AlGaP, InGaP, GaSb, InSb, InAs, InAsSb, AlGaSb, AlSb, InGaSb, AlGaAsSb, InGaAsSb, SiC, Ga2O3, and BN.

[0007] Preferably, the thermal expansion coefficient distribution of the first self-bound exciton polariton layer has a function y=A+B*e x / x 2 Curve distribution; The thermal expansion coefficient distribution of the second self-bound exciton polariton layer has a function y=C+D*x2 +E*sinx curve distribution; thermal expansion coefficient of the lower confinement layer ≥ thermal expansion coefficient of the first self-bound exciton polariton layer ≥ thermal expansion coefficient of the second self-bound exciton polariton layer ≥ thermal expansion coefficient of the lower waveguide layer.

[0008] Preferably, the dielectric constant distribution of the first self-bound exciton polariton layer has a function y=F+G*x -a (a>1 odd number) curve distribution; the dielectric constant distribution of the second self-bound exciton polariton layer has an inverted V-shaped curve distribution; the dielectric constant of the lower confinement layer ≤ the dielectric constant of the first self-bound exciton polariton layer ≤ the dielectric constant of the second self-bound exciton polariton layer ≤ the dielectric constant of the lower waveguide layer.

[0009] The bandgap width distribution of the first self-bound exciton polariton layer has a function y=H+J*a x (a>1) curve distribution; the bandgap width distribution of the second self-bound exciton polariton layer has a V-shaped curve distribution; the bandgap width of the lower confinement layer ≥ the bandgap width of the first self-bound exciton polariton layer ≥ the bandgap width of the second self-bound exciton polariton layer ≥ the bandgap width of the lower waveguide layer.

[0010] The electron affinity energy distribution of the first self-bound exciton polariton layer has a function y=K+L*a x (a>1) curve distribution; the electron affinity energy distribution of the second self-bound exciton polariton layer has a V-shaped curve distribution; the electron affinity of the lower confinement layer ≤ the electron affinity of the first self-bound exciton polariton layer ≤ the electron affinity of the second self-bound exciton polariton layer ≤ the electron affinity of the lower waveguide layer.

[0011] The distribution of thermal expansion coefficient, dielectric constant, bandgap width and electron affinity of the first self-bound exciton polariton layer has the following relationship: H≤C≤A≤K≤F.

[0012] Preferably, 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 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 or Any combination, with a thickness of 10 to 80 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, and BN, with a thickness of 10 to 120 angstroms.

[0013] Preferably, the lower limiting layer, the lower waveguide layer, the upper waveguide layer, and the upper limiting 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, and BN.

[0014] Preferably, the substrate comprises sapphire, silicon, Ge, SiC, AlN, GaN, GaAs, InP, InAs, GaSb, sapphire / SiO2 composite substrate, sapphire / AlN composite substrate, sapphire / SiN x , Sapphire / SiO2 / SiN x Any one of a composite substrate, a magnesium aluminum spinel MgAl2O4, MgO, ZnO, ZrB2, LiAlO2 and LiGaO2 composite substrate.

[0015] Compared with the prior art, a nitride semiconductor laser element provided by an embodiment of the present invention has the following beneficial effects: the self-bound exciton polariton layer has a topological monoclinic periodic ferroelectric domain, forms a strong out-of-plane spontaneous polarization-induced self-bound exciton polariton, increases the free exciton binding energy from less than 10 meV to more than 20 meV, reduces the temperature threshold of the exciton radiation of the laser, and can achieve exciton light radiation at room temperature or higher. At the same time, the self-bound exciton polariton layer couples the topologically protected bound state, the coherent superposition of the coherent exciton polariton condensed state and the incoherent particles, enhances the exciton-assisted stimulated radiation of the laser element, reduces the polarization effect of the active layer, reduces the quantum confined Stark effect, improves the carrier localization and the hole injection and transport efficiency, enhances the peak gain of the laser, reduces the excitation threshold of the laser element, improves the continuous oscillation at room temperature, enhances the confinement factor and gain uniformity, and improves the optical power and slope efficiency of the laser element. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic structural diagram of a nitride semiconductor laser element according to an embodiment of the present invention;

[0017] Figure 2 is a SIMS secondary ion mass spectrum of a nitride semiconductor laser element according to an embodiment of the present invention;

[0018] Reference numerals: 100: substrate; 101: lower confinement layer; 102: lower waveguide layer; 103: active layer; 104: upper waveguide layer, 105: upper confinement layer, 106: self-bound exciton polariton layer, 106a: first self-bound exciton polariton layer, 106b: second self-bound exciton polariton layer. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] In order to solve the above problems, a nitride semiconductor laser element provided in an embodiment of the present application will be introduced and explained in detail through the following specific embodiments.

[0021] Reference Figure 1-2The present invention provides a nitride semiconductor laser element, which includes, from bottom to top, 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. A self-bound exciton polariton layer 106 is provided between the lower waveguide layer 102 and the lower confinement layer 101. The self-bound exciton polariton layer 106 includes a first self-bound exciton polariton layer 106a and a second self-bound exciton polariton layer 106b. The self-bound exciton polariton layer 106 is GaN, InGaN, InN, AlInN, AlGaN, AlInGaN, AlN, InGaN / GaN superlattice, InGaN / AlGaN superlattice , InGaN / AlInGaN superlattice, InGaN / AlInN superlattice, GaN / AlGaN superlattice, GaN / AlInGaN superlattice, GaN / AlN superlattice, GaAs, GaP, InP, AlGaAs, AlInGaAs, AlGaInP, InGaAs, InGaAsN, AlInAs, AlInP, AlGaP, InGaP, GaSb, InSb, InAs, InAsSb, AlGaSb, AlSb, InGaSb, AlGaAsSb, InGaAsSb, SiC, Ga2O3, BN, any one or any combination.

[0022] The thermal expansion coefficient distribution of the first self-bound exciton polariton layer 106a has a function y=A+B*e x / x 2 Curve distribution; The thermal expansion coefficient distribution of the second self-bound exciton polaritons layer 106b has a function y=C+D*x 2 +E*sinx curve distribution; the thermal expansion coefficient of the lower confinement layer 101 ≥ the thermal expansion coefficient of the first self-bound exciton polariton layer 106 a ≥ the thermal expansion coefficient of the second self-bound exciton polariton layer 106 b ≥ the thermal expansion coefficient of the lower waveguide layer 102 .

[0023] The dielectric constant distribution of the first self-bound exciton polariton layer 106a has the function y=F+G*x -a (a>1 odd number) curve distribution; the dielectric constant distribution of the second self-bound exciton polariton layer 106b has an inverted V-shaped curve distribution; the dielectric constant of the lower confinement layer 101 ≤ the dielectric constant of the first self-bound exciton polariton layer 106a ≤ the dielectric constant of the second self-bound exciton polariton layer 106b ≤ the dielectric constant of the lower waveguide layer 102.

[0024] The bandgap width distribution of the first self-bound exciton polariton layer 106a has a function y=H+J*a x(a>1) curve distribution; the bandgap width distribution of the second self-bound exciton polariton layer 106b has a V-shaped curve distribution; the bandgap width of the lower confinement layer 101 ≥ the bandgap width of the first self-bound exciton polariton layer 106a ≥ the bandgap width of the second self-bound exciton polariton layer 106b ≥ the bandgap width of the lower waveguide layer 102.

[0025] The electron affinity distribution of the first self-bound exciton polariton layer 106a has a function y=K+L*a x (a>1) curve distribution; the electron affinity distribution of the second self-bound exciton polariton layer 106b has a V-shaped curve distribution; the electron affinity of the lower confinement layer 101 ≤ the electron affinity of the first self-bound exciton polariton layer 106a ≤ the electron affinity of the second self-bound exciton polariton layer 106b ≤ the electron affinity of the lower waveguide layer 102.

[0026] In summary, the distribution of thermal expansion coefficient, dielectric constant, bandgap width, and electron affinity of the first self-bound exciton polariton layer 106 a has the following relationship: H≤C≤A≤K≤F.

[0027] The self-bound exciton polaritons layer has topological monoclinic periodic ferroelectric domains, forming strong out-of-plane spontaneous polarization induced self-bound exciton polaritons, increasing the free exciton binding energy from less than 10 meV to more than 20 meV, reducing the temperature threshold of the laser exciton radiation, and achieving exciton light radiation at room temperature or higher. At the same time, the self-bound exciton polaritons layer couples topologically protected bound states, coherent superposition of coherent exciton polaritons condensed states and incoherent particles, enhancing the exciton-assisted stimulated radiation of the laser element, reducing the polarization effect of the active layer, reducing the quantum confined Stark effect, improving carrier localization and hole injection and transport efficiency, enhancing the peak gain of the laser, reducing the excitation threshold of the laser element, improving continuous oscillation at room temperature, enhancing the confinement factor and gain uniformity, and improving the optical power and slope efficiency of the laser element. Compared with traditional lasers, the data are as follows:

[0028] Blue Laser Project Conventional laser Laser of the present invention Range of change Slope efficiency (W / A) 0.8 1.37 71％ Optical power(W) 5.1 11.3 122％ Limiting Factor 1.40％ 4.39％ 214％

[0029] In the present invention, 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 any one 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, and BN. 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, and BN, with a thickness of 10 to 120 angstroms.

[0030] 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, and BN.

[0031] In the present invention, the substrate 100 includes sapphire, silicon, Ge, SiC, AlN, GaN, GaAs, InP, InAs, GaSb, sapphire / SiO2 composite substrate, sapphire / AlN composite substrate, sapphire / SiN x , Sapphire / SiO2 / SiN x Any one of a composite substrate, a magnesium aluminum spinel MgAl2O4, MgO, ZnO, ZrB2, LiAlO2 and LiGaO2 composite substrate.

[0032] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A nitride semiconductor laser element, comprising, from bottom to top, 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), characterized in that: A self-bound exciton polariton layer (106) is provided between the lower waveguide layer (102) and the lower confinement layer (101), wherein the self-bound exciton polariton layer (106) comprises a first self-bound exciton polariton layer (106a) and a second self-bound exciton polariton layer (106b); the self-bound exciton polariton layer (106) is GaN, InGaN, InN, AlInN, AlGaN, AlInGaN, AlN, InGaN / GaN superlattice, InGaN / AlGaN superlattice, InGaN / AlInGaN superlattice, InGaN / AlInN superlattice, Lattice, GaN / AlGaN superlattice, GaN / AlInGaN superlattice, GaN / AlN superlattice, GaAs, GaP, InP, AlGaAs, AlInGaAs, AlGaInP, InGaAs, InGaAsN, AlInAs, AlInP, AlGaP, InGaP, GaSb, InSb, InAs, InAsSb, AlGaSb, AlSb, InGaSb, AlGaAsSb, InGaAsSb, SiC, Ga2O3, BN, any one or any combination.

2. The nitride semiconductor laser device according to claim 1, characterized in that: The thermal expansion coefficient distribution of the first self-bound exciton polariton layer (106a) has a function y=A+B*e x / x 2 Curve distribution; The thermal expansion coefficient distribution of the second self-bound exciton polariton layer (106b) has a function y=C+D*x 2 +E*sinx curve distribution; the thermal expansion coefficient of the lower confinement layer (101) ≥ the thermal expansion coefficient of the first self-bound exciton polariton layer (106a) ≥ the thermal expansion coefficient of the second self-bound exciton polariton layer (106b) ≥ the thermal expansion coefficient of the lower waveguide layer (102).

3. The nitride semiconductor laser device according to claim 1, characterized in that: The dielectric constant distribution of the first self-bound exciton polariton layer (106a) has a function y=F+G*x -a (a>1 odd number) curve distribution; the dielectric constant distribution of the second self-bound exciton polariton layer (106b) has an inverted V-shaped curve distribution; the dielectric constant of the lower confinement layer (101) ≤ the dielectric constant of the first self-bound exciton polariton layer (106a) ≤ the dielectric constant of the second self-bound exciton polariton layer (106b) ≤ the dielectric constant of the lower waveguide layer (102).

4. The nitride semiconductor laser device according to claim 1, characterized in that: The bandgap width distribution of the first self-bound exciton polariton layer (106a) has a function y=H+J*a x (a>1) curve distribution; the bandgap width distribution of the second self-bound exciton polariton layer (106b) has a V-shaped curve distribution; the bandgap width of the lower confinement layer (101) ≥ the bandgap width of the first self-bound exciton polariton layer (106a) ≥ the bandgap width of the second self-bound exciton polariton layer (106b) ≥ the bandgap width of the lower waveguide layer (102).

5. The nitride semiconductor laser device according to claim 1, characterized in that: The electron affinity energy distribution of the first self-bound exciton polariton layer (106a) has a function y=K+L*a x (a>1) curve distribution; the electron affinity energy distribution of the second self-bound exciton polariton layer (106b) has a V-shaped curve distribution; the electron affinity energy of the lower confinement layer (101) ≤ the electron affinity energy of the first self-bound exciton polariton layer (106a) ≤ the electron affinity energy of the second self-bound exciton polariton layer (106b) ≤ the electron affinity energy of the lower waveguide layer (102).

6. A nitride semiconductor laser element according to claim 2-5, characterized in that: The thermal expansion coefficient distribution, dielectric constant distribution, bandgap width distribution and electron affinity distribution of the first self-bound exciton polariton layer (106a) have the following relationship: H≤C≤A≤K≤F.

7. The nitride semiconductor laser device according to claim 1, characterized in that: 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 any one 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, and BN or any combination thereof, with a thickness of 10 to 80 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, and BN, with a thickness of 10 to 120 angstroms.

8. The nitride semiconductor laser device according to claim 1, characterized in that: 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, and BN.

9. The nitride semiconductor laser device according to claim 1, characterized in that: The substrate (100) includes sapphire, silicon, Ge, SiC, AlN, GaN, GaAs, InP, InAs, GaSb, sapphire / SiO2 composite substrate, sapphire / AlN composite substrate, sapphire / SiN x , Sapphire / SiO2 / SiN x Any one of a composite substrate, a magnesium aluminum spinel MgAl2O4, MgO, ZnO, ZrB2, LiAlO2 and LiGaO2 composite substrate.

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