Method for manufacturing gallium nitride substrate using the hydride vapor phase epitaxy

Abstract

Disclosed a method of fabricating a gallium nitride substrate using hydride vapor phase epitaxy (HVPE), including a step of injecting ammonia (NH3) gas to perform first surface treatment on a sapphire substrate; a step of injecting ammonia gas and hydrogen chloride (HCl) gas to form a buffer layer on the sapphire substrate; a step of injecting ammonia gas to perform second surface treatment on the sapphire substrate; and a step of allowing gallium nitride (GaN) to grow on the sapphire substrate while lowering the flow rate ratio of ammonia gas to hydrogen chloride gas stepwise.

Description

BACKGROUND OF THE DISCLOSUREField of the Disclosure[0001]The present disclosure relates to a method of fabricating a gallium nitride substrate using hydride vapor phase epitaxy (HVPE), and more particularly, to a method of fabricating a gallium nitride substrate having high quality and a low defect density by preventing bowing and cracking of the gallium nitride substrate.Description of the Related Art[0002]The performance and lifespan of semiconductor devices, such as laser diodes and light emitting diodes, are determined by various factors constituting the device, and are particularly affected by a base substrate on which elements are stacked. Several methods of fabricating a high quality semiconductor substrate have been proposed.[0003]A gallium nitride (GaN) substrate is a typical group III-V compound semiconductor substrate. In addition to a GaAs substrate and an InP substrate, the GaN substrate is suitably used for a semiconductor device. However, the fabrication costs of the ...

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Benefits of technology

[0023]Therefore, the present disclosure has been made in view of the above problems, and it is an object of the present disclosure to provide a method of fabricating a gallium nitride substrate free from bowing and cracking, wherein, when the gallium nitride substrate is fabricated, gallium nitride grows evenly on the surface of a sapphire substrate by allowing gallium nitride (GaN) to grow while lowering the flow rate ratio of ammonia gas to hydrogen chloride gas stepwise, thereby preventing poly gallium nitride (poly GaN) from intensively growing at the edges of the sapphire substrate.

[0024]It is another object of the present disclosure to provide a method of fabricating a gallium nitride substrate having a pit gallium nitride layer similar to a mirror gallium nitride layer thereon, wherein, when the gallium nitride substrate is fabricated, the first and second surface treatments are performed to reduce the surface roughness of a sapphire substrate, thereby allowing a pit gallium nitride layer similar to a mirror gallium nitride layer to grow.

[0025]It is yet another object of the present disclosure to provide a method of fabricating a gallium nitride substrate with reduced occurrence of crystal defects, wherein, when the gallium nitride substrate is fabricated, a large lattice mismatch between a sapphire substrate and gallium nitride is reduced by forming a buffer layer.

[0027]In the step of allowing gallium nitride to grow on the sapphire substrate while lowering the flow rate ratio of ammonia gas to hydrogen chloride gas stepwise, the flow rate of ammonia gas may be lowered stepwise over time and the flow rate of hydrogen chloride gas may be kept constant over time.

Problems solved by technology

However, the fabrication costs of the GaN substrate are much higher than those of the GaAs substrate or the InP substrate.

As a result, cracks occur when growth exceeds a certain thickness, and dislocation occurs at the interface between sapphire and gallium nitride to relax the stress.

The generated dislocation is transmitted in the crystal growth direction, and threading dislocation is transmitted to the growth surface, thus decreasing the crystallinity of the nitride semiconductor substrate and ultimately lowering the electrical characteristics of the device.

However, in the conventional method, since a sapphire substrate is pretreated with HCl before growth, the process is complicated, and the sapphire substrate is damaged (e.g., etched) due to HCl, thereby increasing crystal defects.

Further, since ammonia (NH3) is injected at a relatively high flow rate in the final stage of the process, gallium nitride does not grow uniformly on the surface of the sapphire substrate, and poly gallium nitride (poly GaN) grows intensively at the edges of the sapphire substrate.

However, in the case of the conventional method, gallium nitride does not grow uniformly on the surface of a sapphire substrate, and poly gallium nitride (poly GaN) grows intensively at the edges of the sapphire substrate.

In addition, it is difficult to obtain a low-defect material having high optical quality by allowing gallium nitride to grow to a desired thickness within an allowable range while preventing occurrence of defects in the crystal structure of the grown group III nitride.

However, in the case of the conventional method, it is difficult to obtain a low-defect material having high optical quality by allowing gallium nitride to grow to a desired thickness within an allowable range while preventing occurrence of defects in the crystal structure of the grown gallium nitride semiconductor layer.

However, in the case of the conventional method, the degree of process difficulty increases, and a bowing phenomenon of grown gallium nitride is not completely solved.

However, in the case of the conventional method, since a growth process is performed and then a chemical etching process is performed, an additional process step is required, and gallium nitride may be damaged by excessive chemical etching.

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