阅读说明：本技术 一种提高载流子注入效率的氮化镓基激光器外延结构及其制备方法 (Gallium nitride-based laser epitaxial structure for improving carrier injection efficiency and preparation method thereof ) 是由 赵德刚 杨静 王泓江 于 2020-08-25 设计创作，主要内容包括：本发明提供了一种提高载流子注入效率的氮化镓基激光器外延片结构及其制备方法,属于半导体器件技术领域。外延片结构从下到上包括衬底、高温n型GaN层、高温n型AlGaN限制层、非故意掺杂下波导层、InGaN/GaN多量子阱发光层结构、C掺杂上波导层、p型AlGaN电子阻挡层、p型AlGaN限制层和p型GaN层。本发明通过在上波导层中进行少量的C杂质掺杂,补偿上波导层中的施主缺陷,降低本底载流子浓度,减少载流子在波导层的复合,增加空穴注入效率。(The invention provides a gallium nitride-based laser epitaxial wafer structure for improving carrier injection efficiency and a preparation method thereof, belonging to the technical field of semiconductor devices. The epitaxial wafer structure comprises a substrate, a high-temperature n-type GaN layer, a high-temperature n-type AlGaN limiting layer, an unintentionally doped lower waveguide layer, an InGaN/GaN multi-quantum well light emitting layer structure, a C-doped upper waveguide layer, a p-type AlGaN electron blocking layer, a p-type AlGaN limiting layer and a p-type GaN layer from bottom to top. The invention compensates the donor defect in the upper waveguide layer by doping a small amount of C impurities in the upper waveguide layer, reduces the background carrier concentration, reduces the recombination of carriers in the waveguide layer and increases the hole injection efficiency.)

1. A preparation method of a gallium nitride-based laser epitaxial structure for improving carrier injection efficiency is characterized by comprising the following steps:

annealing the substrate, and removing impurities on the surface of the substrate;

step (2), growing a high-temperature n-type GaN layer on a substrate;

step (3), extending a high-temperature n-type AlGaN limiting layer on the high-temperature n-type GaN layer;

step (4), an unintentionally doped lower waveguide layer is epitaxially grown on the high-temperature n-type AlGaN limiting layer;

step (5), the lower waveguide layer is not doped intentionally to grow an InGaN/GaN multi-quantum well light-emitting layer structure in an epitaxial mode;

step (6), extending a p-type AlGaN electron barrier layer on the InGaN/GaN multi-quantum well light-emitting layer structure;

step (7), epitaxially growing a C-doped upper waveguide layer on the p-type AlGaN electron blocking layer;

and (8) epitaxially growing a p-type GaN layer on the C-doped upper waveguide layer to form a surface ohmic contact layer of the device structure.

2. The method for preparing the epitaxial structure of the GaN-based laser device according to claim 1, wherein the C-doped upper waveguide layer is GaN-based material or InGaN material, the growth temperature is 700 ℃ -1050 ℃, and the thickness is 0.05-0.3 μm.

3. The method as claimed in claim 2, wherein the C source for growing the C-doped upper waveguide layer is trimethyl gallium, triethyl gallium, or trimethyl indium.

4. The method as claimed in claim 2, wherein the concentration of C impurity in the C-doped upper waveguide layer is controlled by adjusting the growth conditions, and the C impurity concentration is in the range of 1 × 10 to improve the carrier injection efficiency¹⁶-1×10¹⁸cm^-3。

5. The method as claimed in claim 1, wherein the growth temperature of the high temperature n-type AlGaN confinement layer is 1000-1200 ℃, the thickness of the high temperature n-type AlGaN confinement layer is 0.5-3 μm, and the Al component is 0.05-0.2.

6. The method for preparing the epitaxial structure of the GaN-based laser device with the improved carrier injection efficiency according to claim 1, wherein the InGaN/GaN multi-quantum well light emitting layer structure comprises 1-5 InGaN/GaN periodic structures, and the light emitting wavelength range is 400 nm-550 nm.

7. The method as claimed in claim 1, wherein the growth temperature of the p-type AlGaN electron blocking layer is 1000-1200 ℃, the thickness of the p-type AlGaN electron blocking layer is 10-20nm, and the Al component is 0.1-0.2.

8. The method as claimed in claim 1, wherein the growth temperature of the p-type AlGaN confinement layer is 1000-1200 ℃, the thickness of the p-type AlGaN confinement layer is 0.1-1 μm, the Al component is 0.05-0.2, and the hole concentration is 1 × 10¹⁷cm^-3-1×10¹⁸cm^-3。

9. The method for preparing the epitaxial structure of GaN-based laser for improving carrier injection efficiency of claim 8, wherein the P-type AlGaN confinement layer can be replaced by a P-type AlGaN/GaN superlattice structure or an AlGaN structure with gradually changed composition.

10. A GaN-based laser epitaxial structure for improving carrier injection efficiency, which is characterized in that the GaN-based laser epitaxial structure prepared by the preparation method of claim 1.

Technical Field

The invention belongs to the technical field of semiconductor devices, and particularly relates to a gallium nitride-based laser epitaxial structure for improving carrier injection efficiency and a preparation method thereof.

Background

The GaN-based material is also called a III-group nitride material (including InN, GaN, AlN, InGaN, AlGaN and the like, the forbidden bandwidth range of the material is 0.7-6.2eV), the spectrum of the material covers the near infrared to deep ultraviolet bands, the material is considered to be a third-generation semiconductor following Si and GaAs, and the material has important application value in the field of optoelectronics. In particular, the GaN-based blue-green laser has important application in the fields of laser illumination, laser projection and the like. As the emission wavelength increases, the refractive index difference between the AlGaN confinement layer and the GaN waveguide layer becomes small, the optical field confinement factor becomes small, and the threshold current of the long wavelength laser significantly increases. In order to increase the optical field limitation, the common long wavelength laser uses InGaN material as the waveguide structure. InGaN growth temperature is low, surface appearance is poor, background carrier concentration is high, but the surface appearance and the carrier concentration of the waveguide layer have important influence on the performance of the laser, the rough surface can cause light scattering, various impurities and defects in the waveguide layer can absorb light, and the recombination of carriers is increased; especially, when the background carrier concentration of the upper waveguide layer is increased, the recombination rate of the upper waveguide layer can be obviously increased, the injection efficiency of holes is reduced, and the performance degradation of the laser device is caused.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides a gallium nitride-based laser epitaxial structure for improving carrier injection efficiency and a preparation method thereof, and solves the problems of high background carrier concentration of a waveguide layer and low hole injection efficiency in a long-wavelength laser.

The present invention achieves the above-described object by the following technical means.

A preparation method of a gallium nitride-based laser epitaxial structure for improving carrier injection efficiency comprises the following steps:

annealing the substrate, and removing impurities on the surface of the substrate;

step (2), growing a high-temperature n-type GaN layer on a substrate;

step (3), extending a high-temperature n-type AlGaN limiting layer on the high-temperature n-type GaN layer;

step (4), an unintentionally doped lower waveguide layer is epitaxially grown on the high-temperature n-type AlGaN limiting layer;

step (5), the lower waveguide layer is not doped intentionally to grow an InGaN/GaN multi-quantum well light-emitting layer structure in an epitaxial mode;

step (6), extending a p-type AlGaN electron barrier layer on the InGaN/GaN multi-quantum well light-emitting layer structure;

step (7), epitaxially growing a C-doped upper waveguide layer on the p-type AlGaN electron blocking layer;

and (8) epitaxially growing a p-type GaN layer on the C-doped upper waveguide layer to form a surface ohmic contact layer of the device structure.

In the technical scheme, the C-doped upper waveguide layer is made of GaN-based materials or InGaN materials, the growth temperature of the C-doped upper waveguide layer is 700-1050 ℃, and the thickness of the C-doped upper waveguide layer is 0.05-0.3 mu m.

In a further technical scheme, the C source for growing the C-doped upper waveguide layer is trimethyl gallium, triethyl gallium or trimethyl indium.

In a further technical scheme, the concentration of the C impurity in the C-doped upper waveguide layer is regulated and controlled by adjusting growth conditions, and the concentration range of the C doping is 1 × 10¹⁶-1×10¹⁸cm^-3。

In the technical scheme, the growth temperature of the high-temperature n-type AlGaN limiting layer is 1000-1200 ℃, the thickness is 0.5-3 μm, and the Al component is 0.05-0.2.

In the technical scheme, the InGaN/GaN multi-quantum well light-emitting layer structure comprises 1-5 InGaN/GaN periodic structures, and the light-emitting wavelength range is 400 nm-550 nm.

In the technical scheme, the growth temperature of the p-type AlGaN electron blocking layer is 1000-1200 ℃, the thickness is 10-20nm, and the Al component is 0.1-0.2.

In the technical scheme, the growth temperature of the p-type AlGaN limiting layer is 1000-1200 ℃, the thickness is 0.1-1 mu m, the Al component is 0.05-0.2, and the hole concentration is 1 × 10¹⁷cm^-3-1×10¹⁸cm^-3。

In a further technical scheme, the P-type AlGaN limiting layer can be replaced by a P-type AlGaN/GaN superlattice structure or an AlGaN structure with gradually changed components.

A gallium nitride-based laser epitaxial structure capable of improving carrier injection efficiency is prepared by the preparation method.

The invention has the beneficial effects that: the invention compensates the donor defect in the upper waveguide layer by doping a small amount of carbon impurities in the upper waveguide layer, reduces the background carrier concentration, reduces the recombination of carriers in the waveguide layer, and increases the hole injection efficiency, thereby reducing the threshold value of the laser, improving the output power of the laser and laying a foundation for preparing a high-performance long-wavelength laser.

Drawings

Fig. 1 is a schematic view of an epitaxial structure of a gan-based laser for improving carrier injection efficiency according to the present invention;

FIG. 2 is a flow chart of a method for fabricating an epitaxial structure of a GaN-based laser for improving carrier injection efficiency according to the present invention;

in the figure: the GaN-based light-emitting diode comprises a substrate 10, a high-temperature n-type GaN layer 11, a high-temperature n-type AlGaN limiting layer 12, an unintentionally doped lower waveguide layer 13, an InGaN/GaN multi-quantum well light-emitting layer structure 14, a p-type AlGaN electron blocking layer 15, a carbon (C) doped upper waveguide layer 16, a p-type AlGaN limiting layer 17 and a p-type GaN layer 18.

Detailed Description

The invention will be further described with reference to the following figures and specific examples, but the scope of the invention is not limited thereto.

As shown in fig. 1, the GaN-based laser epitaxial structure for improving carrier injection efficiency includes, from bottom to top, a substrate 10, a high-temperature n-type GaN layer 11, a high-temperature n-type AlGaN confinement layer 12, an unintentionally doped lower waveguide layer 13, an InGaN/GaN multiple quantum well light emitting layer structure 14, a p-type AlGaN electron blocking layer 15, a carbon (C) -doped upper waveguide layer 16, a p-type AlGaN confinement layer 17, and a p-type GaN layer 18.

As shown in fig. 2, the method for preparing a gan-based laser device with improved carrier injection efficiency specifically includes the following steps:

and (1) heating the substrate 10, annealing the substrate 10 in a hydrogen atmosphere, and removing impurities on the surface of the substrate 10.

Step (2) of growing a high-temperature n-type GaN layer 11 on the substrate 10.

And (3) extending a high-temperature n-type AlGaN limiting layer 12 on the high-temperature n-type GaN layer 11 in an epitaxial manner, wherein the growth temperature of the high-temperature n-type AlGaN limiting layer 12 is 1000-1200 ℃, the thickness of the high-temperature n-type AlGaN limiting layer is 0.5-3 mu m, and the Al component is 0.05-0.2.

And (4) epitaxially growing an unintentionally doped lower waveguide layer 13 on the high-temperature n-type AlGaN limiting layer 12, and limiting light in the waveguide layer by utilizing the refractive index difference between the high-temperature n-type AlGaN limiting layer 12 and the unintentionally doped lower waveguide layer 13.

And (5) epitaxially growing an InGaN/GaN multi-quantum well light-emitting layer structure 14 on the unintentionally doped lower waveguide layer 13, wherein the InGaN/GaN multi-quantum well light-emitting layer structure 14 comprises 1-5 InGaN/GaN periodic structures, and the light-emitting wavelength range is 400 nm-550 nm.

And (6) epitaxially growing a p-type AlGaN electron blocking layer 15 on the InGaN/GaN multi-quantum well light-emitting layer structure 14, wherein the growth temperature of the p-type AlGaN electron blocking layer 15 is 1000-.

And (7) epitaxially growing a carbon (C) -doped upper waveguide layer 16 on the p-type AlGaN electron blocking layer 15, wherein the C-doped upper waveguide layer 16 is made of a GaN-based material or an InGaN material, the growth temperature is 700-1050 ℃, and the thickness is 0.05-0.3 mu m.

Because a certain amount of impurities are introduced in the growth process of the GaN-based material, some vacancy defects such as V are formed_GaSo as to cause the unintentionally doped GaN-based material to be n-type; the background carrier concentration of the general high-temperature growth GaN-based material can reach 10¹⁵-10¹⁶cm^-3(ii) a For InGaN materials, the background carrier concentration is typically greater than 10 due to the low growth temperature¹⁷cm^-3When the In composition is > 0.05, the background carrier concentration of the InGaN material may even exceed 10¹⁸cm^-3(ii) a As a waveguide layer of a GaN-based blue-green light laser, the In component generally needs to be between 0.02 and 0.06, and the excessively high background carrier concentration can increase the recombination rate of the waveguide layer on one hand and change the position of a depletion region on the other hand, so that a light emitting region of a quantum well deviates from the depletion region; finally, the concentration of holes in the trap is reduced, which is not beneficial to improving the performance of the laser.

When (In) GaN is grown by a general MOCVD (metal organic chemical vapor deposition) device, trimethyl gallium, triethyl gallium, trimethyl indium and the like are used as organic sources, and C impurities are generated In the decomposition process of the organic sources, and part of the C impurities are incorporated into an InGaN material. N-type material containing C impurityOn the other hand, the background carrier concentration of InGaN material is changed with In component, so that the C impurity concentration In C-doped upper waveguide layer 16 is changed with In component of (In) GaN material, when In component of (In) GaN material is low, growth temperature is higher, C impurity concentration is lower, when In component of (In) GaN material is high, C impurity concentration is required to be higher, C impurity concentration In C-doped upper waveguide layer 16 is regulated and controlled by regulating growth condition (such as growth pressure, proportion of five-group source and three-group source, growth rate and the like), and C impurity concentration range is 1 × 10¹⁶-1×10¹⁸cm^-3To ensure that the carrier concentration in the C-doped upper waveguide layer 16 is lower than 1 × 10¹⁷cm^-3。

Step (8), epitaxially growing a p-type AlGaN limiting layer 17 on the p-type AlGaN electron blocking layer 15, and limiting light in the waveguide layer by using the refractive index difference between the p-type AlGaN limiting layer 17 and the C-doped upper waveguide layer 16, wherein the growth temperature of the p-type AlGaN limiting layer 17 is 1000-1200 ℃, the thickness is 0.1-1 μm, the Al component is 0.05-0.2, and the hole concentration is 1 × 10¹⁷cm^-3-1×10¹⁸cm^-3(ii) a In order to reduce the series resistance of the device and improve the performance of the device, the P-type AlGaN limiting layer 17 can also be changed into a P-type AlGaN/GaN superlattice structure or an AlGaN structure with gradually changed components.

And (9) epitaxially growing a p-type GaN layer 18 on the p-type AlGaN limiting layer 17 to form a surface ohmic contact layer of the device structure.

The present invention is not limited to the above-described embodiments, and any obvious improvements, substitutions or modifications can be made by those skilled in the art without departing from the spirit of the present invention.