The investigation of in situ removal of Si substrates for freestanding GaN crystals by HVPE

We investigate the etching of a Si substrate in the fabrication process of freestanding GaN crystal grown using a Si by HVPE. Followed by crystal growth, Si etching by vapor HCl at high temperature results in successful fabrication of the freestanding GaN. Due to the complicated vertical gas flows inside the reactor, careful design of the susceptor was implemented. The unintentional formation of Si(x)N(y) thin layer at the backside of the Si substrate after the epitaxial growth, which can cause the decreased etch rate and non-uniform etching of a Si substrate, was successfully prevented by N(2) purging during and after the etching of a Si substrate. We believe that this study will guide us to achieve the growth of freestanding GaN over 8-inch diameters in the efficient and practical way.