# Free-standing 2-inch bulk GaN crystal fabrication by HVPE using a carbon buffer layer

## TL;DR

This paper reports a method for fabricating free-standing 2-inch bulk GaN crystals using HVPE with a carbon buffer layer, enabling self-separation from the substrate and resulting in high-quality crystals.

## Contribution

It introduces a novel HVPE process with an in situ carbon buffer layer for producing large, free-standing GaN crystals with low dislocation density.

## Key findings

- Achieved 365 μm thick, 50 mm diameter free-standing GaN crystals.
- Dislocation density of 8×10^6 cm^-2.
- X-ray rocking curve FWHM of 164 arcsec indicating high crystal quality.

## Abstract

A free-standing bulk gallium nitride layer with a thickness of 365 $\mu$m and a diameter of 50 mm was obtained by hydride vapor phase epitaxy on a sapphire substrate with a carbon buffer layer. The carbon buffer layer was deposited by thermal decomposition of methane $\textit{in situ}$ in the same process with the growth of a bulk GaN layer. The bulk GaN layer grown on the carbon buffer layer self-separated from the sapphire substrate during the cooling after the growth. The dislocation density was $8\cdot10^{6}$ cm$^{-2}$. The (0002) X-Ray rocking curve full width at half maximum was 164 arcsec.