Gallium nitride based LED epitaxial substrate and preparing process thereof

Abstract

The invention provides a gallium nitride based light-emitting diode epitaxial substrate and a method for preparing the same. The method comprises the following steps: (1) depositing a layer of film made of a low-refractive-index material; (2) preparing a mask graph on the film by using a photoresist; (3) transferring patterns of a photoresist mask to the film through etching; and (4) cleaning the substrate to remove the residual photoresist, wherein the substrate is one of sapphire, silicon, silicon carbide, gallium arsenide and zinc oxide, the film is one of the materials of silicon dioxide, silicon nitride, silicon oxynitride or titanium dioxide and the like, the thickness of the film is between 0.1 micro-millimeter and 3 micrometers, the refractive index of the film is less than 2.5, and the substrate pattern is approximately semispherical, conical or round platform shaped. By adopting the gallium nitride based light-emitting diode epitaxial substrate, the light-emitting efficiency of a diode can be improved, the preparation process is easy to control, the preparation method is simple and various, the yield is high, and the production cost is reduced.

Description

technical field [0001] The invention relates to a gallium nitride (GaN)-based light-emitting diode (LED) and a preparation method thereof, in particular to a gallium nitride-based light-emitting diode (LED) epitaxial substrate and a preparation method thereof. Background technique [0002] Gallium nitride-based light-emitting diodes commonly used in the world are mainly heteroepitaxy on a flat substrate, where the substrate can be sapphire, silicon carbide or silicon. The main disadvantages of this structure are: 1. Since there is no lattice matching GaN-based light-emitting diodes are grown on substrates such as sapphire, silicon carbide, or silicon. The difference in lattice constants causes many dislocations in the epitaxial materials. These defects limit the light-emitting diodes. 2. When light enters the substrate from the epitaxial layer, because the interface is relatively flat, the incident angle of light is relatively small, and the refractive index difference betwe...

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Problems solved by technology

[0002] Gallium nitride-based light-emitting diodes commonly used in the world are mainly heteroepitaxy on a flat substrate, where the substrate can be sapphire, silicon carbide or silicon. The main disadvantages of this structure are: 1. Since there is no lattice matching GaN-based light-emitting diodes are grown on substrates such as sapphire, silicon carbide, or silicon. The difference in lattice constants causes many dislocations in the epitaxial materials. These defects limit the light-emitting diodes. 2. When light enters the substrate from the epitaxial layer, because the interface is relatively flat, the incident angle of light is relatively small, and the refractive index difference between gallium nitride and the substrate is not large, resulting in low reflectivity, and most of the light will Escape to the substrate and cannot be effectively reflected back to the epitaxial layer, which greatly reduces the light extraction efficiency of GaN-based light-emitting diodes, especially the refractive index of the substrate of GaN-based blue-green light-emitting diodes with silicon carbide as the substrate. Gallium Nitride is comparable, 100% chance of light escaping from the epitaxial layer to the substrate

[0004] 1. Since the refractive index of sapphire is 1.8, which is relatively close to that of gallium nitride, when light enters the graphics substrate from the epitaxial layer, the reflectivity does not increase significantly, and the improvement of the light output rate of GaN-based light-emitting diodes is not as expected Effect

[0005] 2. Since the sapphire substrate is relatively hard, the production process has high requirements on equipment and technology, especially the dry etching of sapphire requires a helium cooling system and high-density plasma. Ordinary etching equipment cannot meet the requirements. Similarly, wet etching requires the use of strong acid at high temperature, and the production process is difficult to control, resulting in low yield and increased production costs.

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