阅读说明：本技术 一种深紫外led外延结构及其制备方法 (Deep ultraviolet LED epitaxial structure and preparation method thereof ) 是由 丁涛 周飚 郭丽彬 齐胜利 于 2021-09-02 设计创作，主要内容包括：本发明提供一种应用于深紫外发光二极管的外延结构及制备方法,具体步骤如下：提供一平片衬底；生长AlN缓冲层；对AlN缓冲层进行等离子体预处理；生长AlN低温层；生长AlN高温层；生长n型AlGaN层；生长Al-(x)Ga-(1-x)N/Al-(y)Ga-(1-y)N多量子阱有源层；生长Mg掺杂的p型AlGaN层,Mg掺杂的p型AlGaN层和Mg掺杂的p型GaN层。通过等离子体轰击AlN缓冲层表面以在AlN缓冲层铺上一层气体原子,AlN缓冲层所铺上的一层气体原子改变了AlN缓冲层表面的极性,使得后续在AlN缓冲层沉积吸附的AlN的晶体原子排列较为整齐,从而减少了外延层中的晶体缺陷,改善AlN薄膜的晶体质量,减少穿透位错,提升深紫外发光二极管的光电性能。(The invention provides an epitaxial structure applied to a deep ultraviolet light-emitting diode and a preparation method thereof, which comprises the following steps: providing a flat substrate; growing an AlN buffer layer; carrying out plasma pretreatment on the AlN buffer layer; growing an AlN low-temperature layer; growing an AlN high-temperature layer; growing an n-type AlGaN layer; growing Al x Ga 1‑x N/Al y Ga 1‑y N multiple quantum well active layers; and growing a Mg-doped p-type AlGaN layer, a Mg-doped p-type AlGaN layer and a Mg-doped p-type GaN layer. Bombarding the surface of the AlN buffer layer by plasma to lay a layer of gas atoms on the AlN buffer layerThe polarity of the surface of the AlN buffer layer is changed by the gas atoms in one layer, so that AlN crystal atoms deposited and adsorbed on the AlN buffer layer are arranged orderly, the crystal defects in the epitaxial layer are reduced, the crystal quality of the AlN thin film is improved, the threading dislocation is reduced, and the photoelectric performance of the deep ultraviolet light-emitting diode is improved.)

1. A preparation method of a deep ultraviolet LED epitaxial structure is characterized by comprising the following steps:

s1, placing the flat substrate (1) in MOCVD equipment, namely metal organic chemical vapor deposition equipment, and growing an AlN buffer layer (2) on the flat substrate (1);

s2, taking the flat substrate (1) with the AlN buffer layer (2) from the MOCVD equipment, putting the flat substrate into Physical Vapor Deposition (PVD) equipment, and carrying out plasma pretreatment on the upper surface of the AlN buffer layer (2);

s3, placing the flat substrate (1) after plasma pretreatment in MOCVD equipment, and growing an AlN low-temperature layer (3), an AlN high-temperature layer (4), an n-type AlGaN layer (5) and Al on the AlN buffer layer (2) in sequence_xGa_1-xN/Al_yGa_1-yN multi-quantum well active layer (6), Mg-doped p-type AlGaN barrier layer (7), Mg-doped p-type AlGaN layer (8) and Mg-doped p-type GaN layer (9), wherein x is<y；

And S4, annealing in a pure nitrogen atmosphere to obtain the deep ultraviolet LED epitaxial structure.

2. The method for preparing the deep ultraviolet LED epitaxial structure according to claim 1, wherein the flat substrate (1) is one of sapphire, silicon or silicon carbide, and has a thickness of 100-1500 nm.

3. The method for preparing the deep ultraviolet LED epitaxial structure according to claim 1, wherein the AlN buffer layer (2) in the step S1 has a thickness of 1-100nm, a growth temperature of 1000-.

4. The method for preparing the deep ultraviolet LED epitaxial structure of claim 1, wherein the reaction gas of the plasma pretreatment in the step S2 is a mixed gas of nitrogen and oxygen, the process temperature is 100-600 ℃, the pressure is 0.1-5mbar, the electric field is an alternating electric field, and the power of the electric field is 10-100W.

5. The method for preparing the deep ultraviolet LED epitaxial structure according to claim 4, wherein the mixed gas is formed by introducing nitrogen and oxygen together, the introduction amount of the nitrogen is 50-200sccm, and the introduction amount of the oxygen is 1-20 sccm; or the mixed gas is formed by alternately introducing nitrogen and oxygen in a pulse mode, wherein the introduction amount of the nitrogen is 50-200sccm, the introduction time is 1-10s, the introduction amount of the oxygen is 1-20sccm, the introduction time is 1-10s, the primary nitrogen and the primary oxygen form a period, and the cycle number is 10-50.

6. The method for preparing the deep ultraviolet LED epitaxial structure of claim 1, wherein in step S3, the AlN low-temperature layer (3) has a thickness of 100-.

7. The method for preparing the deep ultraviolet LED epitaxial structure according to claim 1, wherein in step S4, the AlN high-temperature layer (4) has a thickness of 1-5 μm, a growth temperature of 1200-.

8. The method for preparing the deep ultraviolet LED epitaxial structure of claim 1, wherein the thickness of the n-type AlGaN layer (5) in step S5 is 100-1000nm, the growth pressure is 10-200mbar, and the Si doping concentration in the layer is 1 x 10¹⁷/cm³-9×10¹⁸/cm³And the Al component is 40-80 wt%.

9. The method for preparing the deep ultraviolet LED epitaxial structure according to claim 1, wherein the Al in the step S6_xGa_1-xN/Al_yGa_1-yN multiple quantum well active layer (6) (x)<y) is nitrogen gas, the growth pressure is 10-200mbar, the growth temperature is 1000-_xGa_1-xN quantum well layer and Al_yGa_1-yThe N quantum barrier layers are alternately grown, wherein the content of the N quantum barrier layers is 35 percent<x<55％、35％<y<55％，x<y; one quantum barrier layer and one quantum well layer form a growth cycle, and the cycle number is 2-10.

10. A deep ultraviolet LED epitaxial structure made by the method of manufacture of any one of claims 1 to 9.

Technical Field

The invention relates to the field of semiconductor materials, in particular to a deep ultraviolet LED epitaxial structure and a preparation method thereof.

Background

With the development of LED application, the market demand of the ultraviolet LED is larger and larger, and the ultraviolet LED with the light-emitting wavelength covering 210 and 400nm has incomparable advantages compared with the traditional ultraviolet light source. The ultraviolet LED can be used in the field of illumination, can replace the traditional ultraviolet mercury lamp containing toxic and harmful substances in the aspects of biological medical treatment, anti-counterfeiting identification, air, water quality purification, biochemical detection, high-density information storage and the like, and has very wide market prospect under the background of the current LED.

At present, an ultraviolet LED epitaxial growth technology is not mature enough, the preparation of materials for growing high-performance ultraviolet LEDs is difficult, the doping difficulty of a p layer is high, the luminous efficiency of a luminous region is low, and the like, so that the luminous efficiency of an ultraviolet LED chip is low, the preparation cost is high, the difficulty is high, and the yield is low.

In order to improve the light emitting efficiency of the AlGaN-based deep ultraviolet LED, how to improve the crystal quality of the AlGaN material is one of important research points. Because of the shortage of the homogeneous substrate, the group III nitride material is usually heteroepitaxially grown on the sapphire substrate, and in order to reduce the dislocation density of the AlGaN material and improve the crystal quality thereof, a layer of binary AlN material needs to be grown on the sapphire first before the AlGaN material is grown. On one hand, the binary AlN material does not have the problem of component segregation in the ternary AlGaN material, and the AlN material crystal growing at high temperature has better quality; on the other hand, the lattice constant of the AlGaN material is larger than that of the AlN material, and the AlGaN material grown on the AlN material is subjected to compressive stress from the AlN material, so that cracking due to excessive thickness of the AlGaN material can be prevented. Therefore, improving the crystal quality of AlN epitaxial layers is a prerequisite for increasing the light-emitting efficiency of deep-ultraviolet LEDs.

Disclosure of Invention

The invention provides a preparation method of a deep ultraviolet LED epitaxial structure, aiming at overcoming the defects of high dislocation density and poor crystal quality of an AlGaN material of the deep ultraviolet LED epitaxial structure in the prior art.

In order to solve the technical problem, the technical scheme is that the preparation method of the deep ultraviolet LED epitaxial structure comprises the following steps:

s1, placing the flat substrate in MOCVD equipment, namely metal organic chemical vapor deposition equipment, and growing an AlN buffer layer on the flat substrate;

s2, taking the flat substrate with the AlN buffer layer out of the MOCVD equipment, putting the flat substrate into physical vapor deposition equipment, namely PVD equipment, and carrying out plasma pretreatment on the upper surface of the AlN buffer layer;

s3, placing the flat substrate after plasma pretreatment in MOCVD equipment, and growing an AlN low-temperature layer, an AlN high-temperature layer, an n-type AlGaN layer and Al on the AlN buffer layer in sequence_xGa_1-xN/Al_yGa_1-yN multi-quantum well active layer, Mg doped p-type AlGaN barrier layer, Mg doped p-type AlGaN layer and Mg doped p-type GaN layer, wherein x is<y；

And S4, annealing in a pure nitrogen atmosphere to obtain the deep ultraviolet LED epitaxial structure.

The preparation method of the deep ultraviolet LED epitaxial structure is further improved as follows:

preferably, the flat substrate (1) is one of sapphire, silicon or silicon carbide, and the thickness is 100-1500 nm.

Preferably, the AlN buffer layer (2) in the step S1 has a thickness of 1-100nm, a growth temperature of 1000-1100 ℃, a growth pressure of 10-200mbar, ammonia gas and trimethylaluminum (i.e. TMAl) are introduced as reactants, and the molar ratio of the reaction gas source V/III is 100-300.

Preferably, the reaction gas for the plasma pretreatment in step S2 is a mixed gas of nitrogen and oxygen, the process temperature is 100-.

Preferably, the mixed gas is formed by introducing nitrogen and oxygen together, wherein the introduction amount of the nitrogen is 50-200sccm, and the introduction amount of the oxygen is 1-20 sccm; or the mixed gas is formed by alternately introducing nitrogen and oxygen in a pulse mode, wherein the introduction amount of the nitrogen is 50-200sccm, the introduction time is 1-10s, the introduction amount of the oxygen is 1-20sccm, the introduction time is 1-10s, the primary nitrogen and the primary oxygen form a period, and the cycle number is 10-50.

Preferably, in the step S3, the AlN low-temperature layer (3) has a thickness of 100-.

Preferably, in the step S4, the AlN high-temperature layer (4) has a thickness of 1-5 μm, a growth temperature of 1200-1400 ℃, a growth pressure of 10-100mbar, a two-dimensional growth mode, ammonia gas and trimethylaluminum are introduced as reactants, a molar ratio of a reaction gas source V/III is 200-400, and a process time is 100-10000S.

Preferably, the thickness of the n-type AlGaN layer (5) in the step S5 is 100-1000nm, the growth pressure is 10-200mbar, and the doping concentration of Si in the layer is 1 × 10¹⁷/cm³-9×10¹⁸/cm³And the Al component is 40-80 wt%.

Preferably, Al is described in step S6_xGa_1-xN/Al_yGa_1-yN multiple quantum well active layer (6) (x)<y) is nitrogen gas, the growth pressure is 10-200mbar, the growth temperature is 1000-_xGa_1-xN quantum well layer and Al_yGa_1-yThe N quantum barrier layers are alternately grown, wherein the content of the N quantum barrier layers is 35 percent<x<55％、35％<y<55％，x<y; one quantum barrier layer and one quantum well layer form a growth cycle, and the cycle number is 2-10.

In order to solve the technical problem, the technical scheme is that the deep ultraviolet LED epitaxial structure is prepared by any one of the preparation methods.

Compared with the prior art, the invention has the beneficial effects that:

according to the invention, after an AlN buffer layer grows on a substrate by MOCVD, plasma pretreatment is carried out on an AlN thin film by PVD, the surface of the AlN thin film is bombarded by plasma to lay a layer of gas atoms on the surface of the AlN thin film, the polarity of the surface of the AlN thin film is changed by the layer of gas atoms laid on the surface of the AlN thin film, so that the AlN thin film presents uniform Al polarity, and the crystal atoms of the AlN thin film grown in MOCVD subsequently are arranged orderly, thereby reducing the crystal defects in an epitaxial layer, improving the crystal quality of the AlN thin film, reducing the threading dislocation and improving the photoelectric performance of the deep ultraviolet light-emitting diode. The Mg-doped P-type AlGaN barrier layer is an electron barrier layer, the Mg-doped P-type AlGaN layer is a hole transport layer, the Mg-doped P-type GaN layer is a P electrode ohmic contact layer, and the layers are matched with each other, so that the luminous efficiency of the deep ultraviolet LED is finally improved.

Drawings

FIG. 1 is a block diagram of the present invention;

fig. 2 is a graph of a two-crystal diffraction analysis of the epitaxial structure of the deep ultraviolet LED prepared in comparative example 1 and examples 1 and 2; wherein (a) is comparative example 1, (b) is example 1, and (c) is example 2.

The designations in the drawings have the following meanings:

1. a flat substrate; 2. an AlN buffer layer; 3. an AlN low-temperature layer; 4. an AlN high-temperature layer; 5. an n-type AlGaN layer; 6. al (Al)_xGa_{1- x}N/Al_yGa_1-yN multiple quantum well active layers; 7. a Mg-doped p-type AlGaN barrier layer; 8. a Mg-doped p-type AlGaN layer; 9. a Mg-doped p-type GaN layer.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to embodiments, and all other embodiments obtained by a person of ordinary skill in the art without any creative effort based on the embodiments of the present invention belong to the protection scope of the present invention.

This example uses high purity hydrogen or nitrogen as carrier gas, trimethyl gallium (TMGa), triethyl gallium (TEGa), trimethyl aluminum (TMAl) and ammonia (NH)₃) Using Silane (SiH) as the source of Ga, Al and N, respectively₄) And magnesium diclometers (Cp)₂Mg) as n-and p-type dopants, respectively.

Comparative example 1

The comparative example provides an epitaxial structure applied to a deep ultraviolet light emitting diode and a preparation method thereof, and the preparation method comprises the following steps:

s1, cleaning the sapphire to be used as a growth substrate 1;

s2, growing the AlN buffer layer 2, wherein the MOCVD process temperature is 1050 ℃, the growth pressure is 50mbar, ammonia gas and trimethylaluminum are introduced as reactants, the V/III molar ratio is 200, the process time is 50S, and the growth thickness is 50 nm;

s3, growing an AlN low-temperature layer 3; the MOCVD process temperature is 1100 ℃, the growth pressure is 60mbar, the molar ratio of introduced ammonia gas and trimethylaluminum as reactants V/III is 3500, and the process time is 500 s;

s4, growing the AlN high-temperature layer 4, wherein the MOCVD process temperature is 1300 ℃, the growth pressure is 50mbar, ammonia gas and trimethylaluminum are introduced as reactants, the V/III molar ratio is 350, and the process time is 5000S;

s5, growing an n-type AlGaN layer 5, wherein the MOCVD process temperature is 1060 ℃, the growth pressure is 100mbar, the growth thickness is 700nm, and the Si doping concentration in the layer is 5 multiplied by 10¹⁸/cm³The Al component is 50 wt%;

s6, growing Al_xGa_1-xN/Al_yGa_1-yN multiple quantum well active layer 6, the MOCVD process temperature is 1040 ℃, the growth atmosphere is nitrogen, the growth pressure is 150mbar, the light-emitting wavelength range is 260-280nm, wherein 35 percent<x<55％、35％<y<55％，x<y; a quantum barrier layer and a quantum well layer are in one growth cycle, and the quantum well layer is Al_xGa_1-xN layer and barrier layer Al_yGa_1-yThe thicknesses of the N layers are respectively 3nm and 11nm, and the periodicity is 2-10;

s7, growing a layer of Mg-doped p-type AlGaN barrier layer 7 at the temperature of 980 ℃ and the growth pressure of 150mbar, wherein the thickness of the layer is 10 nm;

s8, growing a layer of Mg-doped p-type AlGaN layer 8 at the temperature of 900 ℃ and the growth pressure of 200mbar, wherein the thickness of the layer is 25 nm;

s9, growing a layer of Mg-doped p-type GaN layer 9 with the thickness of 50nm at the temperature of 850 ℃ and the growth pressure of 300 mbar;

and S10, annealing for 30 minutes in a nitrogen atmosphere, and finishing the epitaxial growth process to obtain the common deep ultraviolet LED epitaxial structure.

Example 1

The embodiment of the invention provides an epitaxial structure applied to a deep ultraviolet light-emitting diode and a preparation method thereof, and the specific preparation steps refer to comparative example 1, except that the following steps are added between the step S2 and the step S3: the flat substrate 1 with the AlN buffer layer 2 is placed into physical vapor deposition equipment, namely PVD equipment, for plasma pretreatment, nitrogen and oxygen are alternately introduced in a pulse mode, the introduction amount of the nitrogen is 150sccm, the introduction time is 5s, the introduction amount of the oxygen is 5sccm, the introduction time is 5s, one-time nitrogen and one-time oxygen form a period, and the number of pulse periods is 10. The power of an alternating electric field applied by the cavity is 50W, the process temperature is 450 ℃, and the pressure is 4mTorr ";

and finally, manufacturing the deep ultraviolet LED epitaxial structure 1.

Example 2

The embodiment of the invention provides an epitaxial structure applied to a deep ultraviolet light-emitting diode and a preparation method thereof, and the specific preparation steps refer to comparative example 1, except that the following steps are added between the step S2 and the step S3: putting the flat substrate 1 with the AlN buffer layer 2 in physical vapor deposition equipment, namely PVD equipment, for plasma pretreatment, and simultaneously introducing nitrogen and oxygen, wherein the introduction amount of the nitrogen is 100sccm, the introduction amount of the oxygen is 10sccm, the power of an alternating electric field applied by a cavity is 60W, the process temperature is 450 ℃, and the pressure is 4.5 mTorr;

and finally, manufacturing the deep ultraviolet LED epitaxial structure 2.

The epitaxial structures of the deep ultraviolet LED prepared in comparative example 1 and examples 1 and 2 were subjected to XRD:002 twinned diffraction analysis and XRD:102 twinned diffraction analysis, respectively, and the analysis patterns are shown in fig. 2, wherein fig. 2(a) shows comparative examples 1 and 2(b) shows experimental examples 1 and 2(c) shows example 2, the upper curve is 102(XRC), and the lower curve is 002 (XRC). As can be seen from fig. 2, the full widths at half maximum of the deep ultraviolet LED epitaxial structures (002) prepared in examples 1 and 2 are slightly increased, but the full widths at half maximum of (102) are significantly decreased, so that the crystal quality of the AlN material is improved.

It should be understood by those skilled in the art that the foregoing is only illustrative of several embodiments of the invention, and not of all embodiments. It should be noted that many variations and modifications are possible to those skilled in the art, and all variations and modifications that do not depart from the gist of the invention are intended to be within the scope of the invention as defined in the appended claims.