CN106328782A - LED epitaxial structure with composite buffer layer - Google Patents

Abstract

An LED epitaxial structure with a composite buffer layer relates to the technical field of light emitting diode epitaxial. The structure of the present invention includes a sapphire substrate layer, a buffer layer, a u-type GaN layer, an n-type GaN layer, a quantum well light-emitting layer, an electron blocking layer and a p-type GaN layer in order from bottom to top. Its structural feature is that the buffer layer is a composite buffer layer. The buffer layer includes a low-temperature buffer layer, a high-temperature GaN layer, and a low-temperature buffer insertion layer or a medium-temperature buffer insertion layer grown sequentially from bottom to top. Compared with the prior art, the present invention lowers the dislocation density by inserting a low-temperature buffer layer or a medium-temperature buffer layer in the high-temperature GaN epitaxial layer, so as to improve the quality of the crystal structure.

Description

A kind of LED epitaxial structure with composite buffer layer

technical field

The invention relates to the technical field of light-emitting diode epitaxy, in particular to an LED epitaxy structure with a composite buffer layer.

Background technique

Due to the lack of thermally stable substrate materials with matching lattice constants and close thermal expansion coefficients, it is very difficult to grow flat, crack-free, high-quality GaN epitaxial layers with low dislocation density. Reducing the defect density is the key to improving the performance and lifetime of GaN-based materials. The lattice mismatch and thermal mismatch between GaN and sapphire are very large. If high-temperature GaN is grown directly on the sapphire substrate, the growth of GaN is a typical three-dimensional growth mechanism. After experiencing the process of island formation, island growth, three-dimensional growth and uneven surface formation, uneven hexagonal pyramid growth patterns will appear, the surface is rough and the crystal quality is poor, and smooth and clean high-quality films cannot be obtained. Not good, the defect density is high, resulting in a high background carrier concentration in the GaN film. In order to grow high-quality GaN materials with flat surfaces on sapphire substrates and improve the crystallization quality and photoelectric properties of GaN epitaxial layers, it was found that growing a buffer layer on sapphire substrates at a lower temperature can alleviate the problems caused by lattice mismatch. The stress in the buffer layer greatly reduces the dislocation and defect density, as shown in Figure 1. Due to the amorphous nature of the low-temperature growth of the buffer layer, the stress caused by the lattice mismatch between GaN and the substrate and the thermal stress caused by the mismatch of the thermal expansion coefficient are released, and then high-temperature hydrogenation is carried out on the basis of the low-temperature buffer layer. Nitriding gives the substrate a good surface.

In the prior art, the process flow of using MOCVD to grow on a sapphire substrate is: first deposit a thin layer of GaN or AlN at a low temperature below 600°C as a buffer layer (buffer), and then use a high temperature above 1000°C in the buffer layer. GaN is grown on the epitaxial layer; this growth can reduce the dislocation density in the epitaxial layer to a certain extent, but the average dislocation density is still as high as 10 ^{8 -10 10} /cm ² , which directly affects the quality of the crystal structure.

Contents of the invention

Aiming at the deficiencies in the above-mentioned prior art, the present invention provides an LED epitaxial structure with a composite buffer layer. It reduces the dislocation density by inserting a low-temperature buffer layer or a medium-temperature buffer layer in the high-temperature GaN epitaxial layer to improve the quality of the crystal structure.

In order to achieve the above-mentioned purpose of the invention, the technical solution of the present invention is realized in the following manner:

An LED epitaxial structure with a composite buffer layer, which sequentially includes a sapphire substrate layer, a buffer layer, a u-type GaN layer, an n-type GaN layer, a quantum well light-emitting layer, an electron blocking layer and a p-type GaN layer from bottom to top. Its structural feature is that the buffer layer is a composite buffer layer. The buffer layer includes a low-temperature buffer layer, a high-temperature GaN layer, and a low-temperature buffer insertion layer or a medium-temperature buffer insertion layer grown sequentially from bottom to top.

In the above LED epitaxial structure, the growth temperature of the low-temperature buffer insertion layer is 500-600° C., the growth pressure is 500-600 Torr, the growth time is 145-195 s, and there is no doping.

In the above-mentioned LED epitaxial structure, the growth temperature of the intermediate temperature buffer insertion layer is 700-900° C., the growth pressure is 500-600 Torr, the growth time is 145-195 s, and there is no doping.

Due to the adoption of the above structure, the present invention inserts a low-temperature buffer insertion layer or a medium-temperature buffer insertion layer between the high-temperature GaN epitaxial layer and the U-shaped GaN layer, which is beneficial to reduce the dislocation density and improve the crystal structure quality.

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

Description of drawings

Fig. 1 is a schematic diagram of LED epitaxial structure in the prior art;

2 is a schematic diagram of an LED epitaxial structure in an embodiment of the present invention;

FIG. 3 is a schematic diagram of another LED epitaxial structure in an embodiment of the present invention.

detailed description

Referring to Fig. 2 and Fig. 3, the LED epitaxial structure with composite buffer layer of the present invention comprises sapphire substrate layer 1, buffer layer 2, u-type GaN layer 3, n-type GaN layer 4, quantum well light-emitting layer 5, Electron blocking layer 6 and p-type GaN layer 7. The buffer layer 2 is a composite buffer layer, and the buffer layer 2 includes a low-temperature buffer layer 21 , a high-temperature GaN layer 22 , and a low-temperature buffer insertion layer 231 or a medium-temperature buffer insertion layer 232 grown sequentially from bottom to top. The growth temperature of the low-temperature buffer insertion layer 231 is 500-600° C., the growth pressure is 500-600 Torr, the growth time is 145-195 s, and there is no doping. The growth temperature of the medium temperature buffer insertion layer 232 is 700-900° C., the growth pressure is 500-600 Torr, the growth time is 145-195 s, and there is no doping.

The concrete growth of buffer layer 2 among the present invention can adopt following several implementation modes:

Embodiment one

Grow the low-temperature buffer layer 21 at a temperature of 550°C and a growth pressure of 550 Torr for 145s; then raise the temperature to 1035°C for 2200s The high-temperature GaN layer 22 is then lowered to grow a low-temperature buffer insertion layer 231 for 145 seconds at a temperature of 500° C. and a growth pressure of 500 Torr.

Embodiment two

The low-temperature buffer layer 21 was grown at a temperature of 550°C and a growth pressure of 550Torr for 145s; the temperature was then raised to 1035°C for 2200s to grow a high-temperature GaN layer 22; and then the temperature was lowered to grow a low-temperature buffer insertion layer 231 for 175s at a temperature of 550°C and a growth pressure of 550Torr.

Embodiment three

The low-temperature buffer layer 21 is grown at a temperature of 550°C and a growth pressure of 550Torr for 145s; the temperature is then raised to 1035°C for 2200s to grow a high-temperature GaN layer 22; and then the temperature is lowered to grow a low-temperature buffer insertion layer 231 for 195s at a temperature of 600°C and a growth pressure of 600Torr.

Embodiment four

The low-temperature buffer layer 21 is grown at a temperature of 550°C and a growth pressure of 550Torr for 145s; the temperature is then raised to 1035°C for 2200s to grow a high-temperature GaN layer 22; and then the temperature is lowered to grow a medium-temperature buffer insertion layer 232 for 145s at a temperature of 700°C and a growth pressure of 500Torr.

Embodiment five

The low-temperature buffer layer 21 is grown at a temperature of 550°C and a growth pressure of 550Torr for 145s; the temperature is then raised to 1035°C for 2200s to grow a high-temperature GaN layer 22; and then the temperature is lowered to grow a medium-temperature buffer insertion layer 232 for 170s at a temperature of 800°C and a growth pressure of 550Torr.

Embodiment six

The low-temperature buffer layer 21 was grown at a temperature of 550°C and a growth pressure of 550Torr for 145s; the temperature was then raised to 1035°C for 2200s to grow a high-temperature GaN layer 22; and then the temperature was lowered to grow a medium-temperature buffer insertion layer 232 for 195s at a temperature of 900°C and a growth pressure of 600Torr.

The above is only a specific embodiment of the present invention, and is not limited to other implementations of the present invention. Any obvious modifications, replacements or improvements made within the technical route principles of the present invention shall belong to the present invention. within the scope of protection of the invention.

Claims (3)

1. the LED epitaxial structure of a band compound buffer layer, it includes Sapphire Substrate layer (1), cushion (2), u-shaped GaN layer (3), n-type GaN layer (4), mqw light emitting layer (5), electronic barrier layer (6) and p-type GaN layer (7) the most successively, it is characterized in that: described cushion (2) is compound buffer layer, cushion (2) includes low temperature buffer layer (21), high-temperature gan layer (22) and low temperature buffer interposed layer (231) or middle temperature buffering interposed layer (232) grown the most successively.

The LED epitaxial structure of band compound buffer layer the most according to claim 1, it is characterised in that: the growth temperature of described low temperature buffer interposed layer (231) is 500-600 DEG C, and growth pressure is 500-600Torr, and growth time is 145-195s, non-impurity-doped.

The LED epitaxial structure of band compound buffer layer the most according to claim 1, it is characterised in that: the growth temperature of described middle temperature buffering interposed layer (232) is 700-900 DEG C, and growth pressure is 500-600Torr, and growth time is 145-195s, non-impurity-doped.