Gallium nitride based near ultraviolet laser with composite waveguide layer
阅读说明：本技术 具有复合波导层的氮化镓基近紫外激光器 (Gallium nitride based near ultraviolet laser with composite waveguide layer ) 是由 陈平 赵德刚 朱建军 刘宗顺 杨静 梁锋 于 2020-03-27 设计创作，主要内容包括：一种具有复合波导层的氮化镓基近紫外激光器包括一衬底；一n型外延层；一n型限制层；一第一n型AlInN波导层；一第二n型AlInN波导层；一有源区；一AlInN波导层；一p型电子阻挡层；一p型AlInN波导层；一p型限制层,其制作在p型AlGaN波导层上,该p型限制层的中间为一凸起的脊形；一p型掺杂/p型重掺接触层；一p型欧姆电极以及一n型欧姆电极。本发明采用AlInN材料代替AlGaN材料作为氮化镓基近紫外激光器的波导层,在同样的生长温度下,AlInN的晶体质量更好,缺陷密度更低,减少了由缺陷和杂质引起的光学吸收。AlInN更容易通过改变组分获得更大的折射率差,将光场更好地限制在有源区附近,增大了激光器的光学限制因子。(A GaN-based near-ultraviolet laser with a composite waveguide layer comprises a substrate; an n-type epitaxial layer; an n-type confinement layer; a first n-type AlInN waveguide layer; a second n-type AlInN waveguide layer; an active region; an AlInN waveguide layer; a p-type electron blocking layer; a p-type AlInN waveguide layer; the p-type limiting layer is manufactured on the p-type AlGaN waveguide layer, and the middle of the p-type limiting layer is provided with a raised ridge; a p-type doped/p-type heavily doped contact layer; a p-type ohmic electrode and an n-type ohmic electrode. The invention adopts AlInN material to replace AlGaN material as the waveguide layer of the GaN-based near ultraviolet laser, and the AlInN crystal has better quality and lower defect density at the same growth temperature, thereby reducing the optical absorption caused by defects and impurities. AlInN more readily achieves a larger refractive index difference by changing the composition, better confines the optical field near the active region, and increases the optical confinement factor of the laser.)
1. A gallium nitride-based near-ultraviolet laser having a composite waveguide layer, comprising:
a substrate;
an n-type epitaxial layer formed on the substrate;
an n-type limiting layer which is made on the n-type epitaxial layer;
a first n-type AlInN waveguide layer formed on the n-type confinement layer;
the second n-type AlInN waveguide layer is manufactured on the first n-type AlInN waveguide layer;
an active region formed on the second n-type AlInN waveguide layer;
an AlInN waveguide layer formed on the active region;
the p-type electron blocking layer is manufactured on the AlInN waveguide layer;
a p-type AlInN waveguide layer formed on the p-type electron blocking layer;
the p-type limiting layer is manufactured on the p-type AlGaN waveguide layer, and the middle of the p-type limiting layer is provided with a raised ridge;
a p-type doped/heavily doped contact layer formed on the raised ridge of the p-type confinement layer;
a p-type ohmic electrode formed on the p-type doped/p-type heavily doped contact layer; and
and the n-type ohmic electrode is manufactured at the bottom of the substrate.
2. The gallium nitride-based near-ultraviolet laser according to claim 1,
the substrate comprises a gallium nitride native substrate, wherein the gallium nitride native substrate is an n-type doped self-supporting gallium nitride material with a thickness of 200 to 1000 μm.
3. The gallium nitride-based near-ultraviolet laser according to claim 1,
the n-type epitaxial layer comprises an n-type GaN homogeneous epitaxial layer, wherein the n-type GaN homogeneous epitaxial layer is Si-doped n-type GaN and has a thickness of 1-10 mu m.
4. The gallium nitride-based near-ultraviolet laser according to claim 1,
the n-type limiting layer comprises an n-type AlGaN limiting layer, wherein the n-type AlGaN limiting layer is Si-doped n-type AlGaN, the Al component is 0.01-1, and the thickness is 10-1000 nm.
5. The gallium nitride-based near-ultraviolet laser according to claim 1,
the first n-type AlInN waveguide layer is Si-doped n-type AlInN, the Al component is 0.01-1, the In component is 0.01-1, and the thickness is 10-300 nm.
6. The gallium nitride-based near-ultraviolet laser according to claim 1,
the second n-type AlInN waveguide layer is Si-doped n-type AlInN, the Al component is 0.01-1, the In component is 0.01-1, and the thickness is 10-300 nm.
7. The gallium nitride-based near-ultraviolet laser according to claim 1,
the active region comprises an InGaN/AlGaN quantum well active region, wherein the InGaN/AlGaN quantum well active region is unintentionally doped InGaN/AlGaN, and the number of periods of quantum wells is 1-5; the well layer is made of InGaN material, the In component is 0.01-1, and the thickness is 1-10 nm; the barrier layer is AlGaN, the Al component is 0.01-1, and the thickness is 5-30 nm.
8. The gallium nitride-based near-ultraviolet laser according to claim 1,
the AlInN waveguide layer is unintentionally doped AlInN, the thickness is 5-100nm, the Al component is 0.01-1, and the In component is 0.01-1;
the p-type electron blocking layer comprises a p-type AlGaN electron blocking layer, wherein the p-type AlGaN electron blocking layer is Mg-doped p-type AlGaN, the Al component is 0.1-0.3, and the thickness is 5-40 nm.
9. The gallium nitride-based near-ultraviolet laser according to claim 1,
the p-type AlInN waveguide layer is Mg-doped p-type AlInN, the Al component is 0.01 to 1, the In component is 0.01 to 1, and the thickness is 10 to 300 nm;
the p-type limiting layer comprises a p-type AlGaN limiting layer, wherein the p-type AlGaN limiting layer is Mg-doped p-type AlGaN, the Al component is 0.01-1, and the thickness is 10-1000 nm.
10. The gallium nitride-based near-ultraviolet laser according to claim 1,
the p-type doped/p-type heavily doped contact layer is of a composite structure of p-type doping and p-type heavily doping;
wherein the p-type doped layer is Mg-doped p-type GaN with a thickness of 10-100nm and a Mg doping concentration of 1 × 1018To 1 × 1020cm-3；
Wherein the p-type heavily doped layer is a p-type GaN or p-type AlGaN layer heavily doped with Mg, the thickness of the p-type heavily doped layer is 5-50nm, the Mg doping concentration is higher than that of the p-type doped layer, and the Mg doping concentration is 1 × 1019To 3 × 1021em-3The p-type AlGaN layer has an Al composition of 0.01 to 1.
Technical Field
The invention relates to the field of semiconductor photoelectronic devices, in particular to a gallium nitride-based near ultraviolet laser with a composite waveguide layer.
Background
The laser wavelength of the gallium nitride-based semiconductor laser theoretically covers a wide range from infrared to ultraviolet bands, and the gallium nitride-based semiconductor laser has wide application in the fields of solid-state lighting, automobile headlights, laser projection and display, biological disinfection and sterilization and the like. The wavelengths of gallium nitride-based lasers that are currently commercialized include blue light, violet light, green light and partial near ultraviolet, and deep ultraviolet lasers with wavelengths as short as 271.8nm have also achieved electro-injection lasing.
The problems faced during the development of near ultraviolet band gan-based lasers are mainly the decrease in the recombination rate of light emission and the increase in the optical absorption loss, compared to the visible band. The wavelength of the near ultraviolet band is short, the In component In the corresponding InGaN quantum well is low, the local state density related to the In component is reduced, and the light emitting recombination rate In the InGaN quantum well is reduced; the reduction of In component leads to the shallow depth of the trap, the limitation action on the current carrier In the trap is weakened, the leakage current is increased, and the quantum efficiency of the active region is reduced. In the aspect of optical absorption loss, the wavelength of the near ultraviolet laser is short, and the limiting effect of the waveguide layer and the limiting layer on an optical field is weakened; in the laser structure, Al components of a quantum barrier layer, a waveguide layer, a limiting layer and a contact layer are increased, the material quality is reduced, the defect density is increased, and the optical absorption loss is increased. The band-edge absorption of GaN native substrates causes severe optical absorption loss when the lasing wavelength of the near-uv laser is close to 362nm, which corresponds to the gallium nitride band gap.
In response to the above problems faced by gallium nitride-based near-ultraviolet lasers, researchers have proposed various solutions. For the reduction of the carrier limiting effect caused by the shallow well depth of the InGaN quantum well, the AlGaN barrier layer can be used for replacing the InGaN or GaN barrier layer, and the barrier height of the quantum well is improved. For increased optical absorption loss, the optical confinement effect can be enhanced by increasing the Al composition in the AlGaN waveguide layer and confinement layer. However, the Al component in the AlGaN quantum barrier layer and the waveguide layer/confinement layer increases, so that the defect density in the laser structure increases, which affects the device performance.
Disclosure of Invention
The invention mainly aims to provide a gallium nitride-based near-ultraviolet laser with a composite waveguide layer, aiming at the problems of the gallium nitride-based laser in a near-ultraviolet band, the AlInN composite waveguide layer is adopted to improve the optical limiting factor of the laser and the light-emitting composite efficiency of a quantum well, reduce the optical absorption loss and improve the performance of the laser.
In order to achieve the above object, the present invention provides a gallium nitride-based near-ultraviolet laser having a composite waveguide layer, comprising:
a substrate;
an n-type epitaxial layer formed on the substrate;
an n-type limiting layer which is made on the n-type epitaxial layer;
a first n-type AlInN waveguide layer formed on the n-type confinement layer;
the second n-type AlInN waveguide layer is manufactured on the first n-type AlInN waveguide layer;
an active region formed on the second n-type AlInN waveguide layer;
an AlInN waveguide layer formed on the active region;
the p-type electron blocking layer is manufactured on the AlInN waveguide layer;
a p-type AlInN waveguide layer formed on the p-type electron blocking layer;
the p-type limiting layer is manufactured on the p-type AlGaN waveguide layer, and the middle of the p-type limiting layer is provided with a raised ridge;
a p-type doped/heavily doped contact layer formed on the raised ridge of the p-type confinement layer;
a p-type ohmic electrode formed on the p-type doped/p-type heavily doped contact layer; and
and the n-type ohmic electrode is manufactured at the bottom of the substrate.
Based on the technical scheme, compared with the prior art, the gallium nitride-based near-ultraviolet laser with the composite waveguide layer has at least one of the following advantages:
1. the invention adopts AlInN material to replace AlGaN material as the waveguide layer of the GaN-based near ultraviolet laser, and the AlInN crystal has better quality and lower defect density at the same growth temperature, thereby reducing the optical absorption caused by defects and impurities. AlInN more readily achieves a larger refractive index difference by changing the composition, better confines the optical field near the active region, and increases the optical confinement factor of the laser.
2. The waveguide layers on the p-type side and the n-type side are both made of two layers of AlInN materials, and the thicknesses of the components are different. And an AlInN waveguide layer is inserted between the InGaN quantum well active region and the p-type doped AlGaN electronic barrier layer on the p-type side, and the AlInN layer is unintentionally doped, so that the p-type doped region is far away from the InGaN quantum well active region. The back diffusion of magnesium impurities can be reduced, and the magnesium impurities are prevented from entering an InGaN quantum well active region; compared with the p-type doped AlGaN electron blocking layer, the unintentionally doped AlInN has larger optical refractive index difference and lower optical absorption coefficient, and can reduce the optical absorption loss near the active region. On the n-type side, the two AlInN waveguide layers provide a larger refractive index difference and a stronger optical confinement effect. The AlInN waveguide layer close to the InGaN quantum well active region can reduce the defect density In the waveguide layer and the surface roughness of the waveguide layer by changing the Al/In components and growth conditions and utilizing the surface catalytic action of In atoms, so that the optical absorption loss caused by an interface state is reduced, and the material quality of the subsequently grown quantum well active region is improved. Therefore, after the AlInN composite waveguide is adopted, the optical absorption loss can be reduced, the light-emitting composite rate of an InGaN quantum well can be improved, the threshold value of a gallium nitride-based near ultraviolet laser can be reduced, and the output characteristic of the laser can be improved.
Drawings
Fig. 1 is a schematic structural diagram of a gan laser according to an embodiment of the present invention.
Detailed Description
In order that the objects, technical solutions and advantages of the present invention will become more apparent, the present invention will be further described in detail with reference to the accompanying drawings in conjunction with the following specific embodiments.
The invention discloses a gallium nitride-based near ultraviolet laser with a composite waveguide layer, which comprises:
a substrate;
an n-type epitaxial layer formed on the substrate;
an n-type limiting layer which is made on the n-type epitaxial layer;
a first n-type AlInN waveguide layer formed on the n-type confinement layer;
the second n-type AlInN waveguide layer is manufactured on the first n-type AlInN waveguide layer;
an active region formed on the second n-type AlInN waveguide layer;
an AlInN waveguide layer formed on the active region;
the p-type electron blocking layer is manufactured on the AlInN waveguide layer;
a p-type AlInN waveguide layer formed on the p-type electron blocking layer;
the p-type limiting layer is manufactured on the p-type AlGaN waveguide layer, and the middle of the p-type limiting layer is provided with a raised ridge;
a p-type doped/heavily doped contact layer formed on the raised ridge of the p-type confinement layer;
a p-type ohmic electrode formed on the p-type doped/p-type heavily doped contact layer; and
and the n-type ohmic electrode is manufactured at the bottom of the substrate.
In some embodiments of the present invention, the substrate comprises a gallium nitride native substrate, wherein the gallium nitride native substrate is an n-type doped free-standing gallium nitride material having a thickness of 200 to 1000 μm.
In some embodiments of the present invention, the n-type epitaxial layer comprises an n-type GaN homoepitaxial layer, wherein the n-type GaN homoepitaxial layer is Si-doped n-type GaN with a thickness of 1 to 10 μm.
In some embodiments of the present invention, the n-type confinement layer comprises an n-type AlGaN confinement layer, wherein the n-type AlGaN confinement layer is Si-doped n-type AlGaN having an Al composition of 0.01 to 1 and a thickness of 10 to 1000 nm.
In some embodiments of the present invention, the first n-type AlInN waveguide layer is Si-doped n-type AlInN, with an Al composition of 0.01 to 1, an In composition of 0.01 to 1, and a thickness of 10 to 300 nm.
In some embodiments of the present invention, the second n-type AlInN waveguide layer is Si-doped n-type AlInN, with an Al composition of 0.01 to 1, an In composition of 0.01 to 1, and a thickness of 10 to 300 nm.
In some embodiments of the present invention, the active region comprises an InGaN/AlGaN quantum well active region, wherein the InGaN/AlGaN quantum well active region is unintentionally doped InGaN/AlGaN, and the number of periods of quantum wells is 1 to 5; the well layer is made of InGaN material, the In component is 0.01-1, and the thickness is 1-10 nm; the barrier layer is AlGaN, the Al component is 0.01-1, and the thickness is 5-30 nm.
In some embodiments of the invention, the AlInN waveguide layer is unintentionally doped AlInN having a thickness of 5 to 100nm, an Al composition of 0.01 to 1, an In composition of 0.01 to 1;
in some embodiments of the present invention, the p-type electron blocking layer comprises a p-type AlGaN electron blocking layer, wherein the p-type AlGaN electron blocking layer is Mg doped p-type AlGaN having an Al composition of 0.1 to 0.3 and a thickness of 5 to 40 nm.
In some embodiments of the invention, the p-type AlInN waveguide layer is Mg doped p-type AlInN, with an Al composition of 0.01 to 1, an In composition of 0.01 to 1, and a thickness of 10 to 300 nm;
in some embodiments of the invention, the p-type confinement layer comprises a p-type AlGaN confinement layer, wherein the p-type AlGaN confinement layer is Mg doped p-type AlGaN having an Al composition of 0.01 to 1 and a thickness of 10 to 1000 nm.
In some embodiments of the invention, the p-type doped/p-type heavily doped contact layer is a composite structure of p-type doping and p-type heavily doping;
in some embodiments of the present invention, the p-type doped layer is Mg-doped p-type GaN with a thickness of 10 to 100nm and a Mg doping concentration of 1 × 1018To 1 × 1020cm-3；
In some embodiments of the invention, the p-type heavily doped layer is a heavily Mg-doped p-type GaN or p-type AlGaN layer with a thickness of 5 to 50nm less than that of the p-type doped layer, and the Mg doping concentration is 1 × 10 higher than that of the p-type doped layer19To 3 × 1021cm-3Of p-type AlGaN layerThe Al component is 0.01 to 1.
The technical solution of the present invention is further illustrated by the following specific embodiments in conjunction with the accompanying drawings. It should be noted that the following specific examples are given by way of illustration only and the scope of the present invention is not limited thereto.
Referring to fig. 1, the present invention provides a gan-based near-uv laser with a composite waveguide layer, including:
a GaN homomorphic substrate 10, wherein the GaN homomorphic substrate 10 is an n-type doped self-supporting GaN material with a thickness of 200-1000 μm;
an n-type GaN homoepitaxial layer 11 which is manufactured on the GaN homoepitaxial substrate 10, wherein the n-type GaN homoepitaxial layer is Si-doped n-type GaN and has the thickness of 1-10 mu m;
the n-type AlGaN limiting layer 12 is manufactured on the n-type GaN homoepitaxial layer 11, the n-type AlGaN limiting layer 12 is Si-doped n-type AlGaN, the Al component is 0.01-1, and the thickness is 10-1000 nm;
a first n-type AlInN waveguide layer 13 formed on the n-type AlGaN confinement layer 12, wherein the first n-type AlInN waveguide layer 13 is Si-doped n-type AlInN, has an Al component of 0.01-1 and a thickness of 10-300 nm. After the AlGaN material is replaced by the AlInN material, the layer has the following three advantages: firstly, In atoms can play a role of a surface catalyst In the epitaxial growth process, the crystal quality of AlInN is higher than that of AlGaN, the defect density is lower, and the optical absorption coefficient is small at the same growth temperature; secondly, AlInN can obtain larger refractive index difference more easily, and can provide stronger optical limiting effect; and thirdly, by adjusting the Al/In composition, the lattice mismatch between the AlInN and the GaN substrate can be reduced, and the stress and dislocation density are reduced.
And a second n-type AlInN waveguide layer 14 which is manufactured on the first n-type AlInN waveguide layer 13, wherein the second n-type AlInN waveguide layer 14 is Si-doped n-type AlInN, the Al component is 0.01-1, and the thickness is 10-300 nm. The second AlInN waveguide layer 14 should have a larger refractive index and a lower surface roughness than the first n-type AlInN waveguide layer 13. The large refractive index provides a greater refractive index difference between the AlInN and first n-type AlInN waveguide layer 13 and the n-type AlGaN confinement layer 12, enhancing optical confinement near the active region. Lower surface roughness and defect density are beneficial for improving the quality of the InGaN quantum well material that continues to grow on the surface of the layer, and reducing optical scattering caused by interface abruptness.
An InGaN/AlGaN quantum well active region 15, which is manufactured on the second n-type AlInN waveguide layer 14, wherein the InGaN/AlGaN quantum well active region is unintentionally doped InGaN/AlGaN, and the number of periods of the quantum well is 1-5; the well layer is made of InGaN material, the In component is 0.01-1, and the thickness is 1-10 nm; the barrier layer is AlGaN, the Al component is 0.01-1, and the thickness is 5-30 nm;
and the AlInN waveguide layer 16 is manufactured on the InGaN/AlGaN quantum well active region 15, and is formed by unintentionally doped AlInN with the thickness of 5-100nm, the Al component of 0.01-1 and the In component of 0.01-1. The insertion of the AlInN waveguide layer firstly leads the p-type doped region to be far away from the InGaN quantum well active region, thereby reducing the optical absorption loss caused by p-type doping; secondly, the back diffusion of the magnesium impurities in the p-type layer to the active region of the quantum well is inhibited; finally, the lattice parameter of AlInN can be matched with or close to GaN by adjusting the Al/In component, so that the lattice mismatch is reduced, and meanwhile, the band gap of AlInN is far away from 3.42eV of GaN, so that the interband absorption is reduced.
And the p-type AlGaN electron blocking layer 17 is manufactured on the AlInN waveguide layer 16, and is Mg-doped p-type AlGaN, the Al component is 0.1-0.3, and the thickness is 5-40 nm.
And the p-type AlInN waveguide layer 18 is manufactured on the p-type AlGaN electron blocking layer 17, the p-type AlInN waveguide layer 18 is Mg-doped p-type AlInN, the Al component is 0.01-1, and the thickness is 10-300 nm. The p-type AlInN waveguide layer 18 has the advantages similar to those of the n-type AlInN waveguide layer 13, and compared with the AlGaN waveguide layer, the crystal quality is high and the defect density is low; the optical refractive index difference is large, and the optical limiting effect is strong; the lattice mismatch is small, and stress and misfit dislocation can be reduced. It should be noted that the p-type AlInN waveguide layer 18 and the AlInN waveguide layer 16 form a composite waveguide on the p-type side, the n-type AlInN waveguide layer 13 and the n-type AlInN waveguide layer 14 form a composite waveguide on the n-type side, and the two composite waveguides are different in composition and thickness. In the laser structure design process, the refractive index difference of the p-type side composite waveguide can be improved by changing the components and the thickness, and the optical limiting effect is enhanced. The p-type and n-type side asymmetric composite waveguide structure can make the optical field distribution properly biased to the n-type side, reduce the optical absorption loss of the p-type side and finally improve the performance of the gallium nitride-based near ultraviolet laser.
The p-type AlGaN limiting layer 19 is manufactured on the p-type AlInN waveguide layer 18, the middle of the p-type AlGaN limiting layer 19 is provided with a raised ridge, the p-type AlGaN limiting layer is Mg-doped p-type AlGaN, the Al component is 0.01-1, and the thickness is 10-1000 nm;
a p-type doped/p-type heavily doped contact layer 20 formed on the raised ridge of the p-type AlGaN confinement layer 19, wherein the p-type doped/p-type heavily doped contact layer is of a composite structure of p-type doping and p-type heavily doping, the p-type doped layer is p-type GaN doped with Mg, the thickness of the p-type doped layer is 10-100nm, and the Mg doping concentration is 1 × 1018-1×1020cm-3The p-type heavily doped layer is a p-type GaN or p-type AlGaN layer heavily doped with Mg, the thickness of the p-type heavily doped layer is 5-50nm, the Mg doping concentration is higher than that of the p-type doped layer, and the Mg doping concentration is 1 × 1019-3×1021cm-3The Al component of the p-type AlGaN layer is 0.01-1;
a p-type ohmic electrode 21 formed on the p-type doped/p-type heavily doped contact layer 20;
an n-type ohmic electrode 22 formed on the lower surface of the GaN homosubstrate 10.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.