Recent progress in HVPE-based GaN substrate fabrication

Using our void-assisted separation (VAS) method based on hydride vapor phase epitaxy (HVPE), a 6-inch free-standing GaN wafer has been successfully realized. Extremely wide range of n-type doping from 1e15 to 1e20 /cm3 is available. High enough thermal conductivity around 150 W/mK, suitable for high-power device operation, was maintained even when the doping concentration was 1e20/cm3. In addition, we will also talk about newly developed method suitable for fabrication of large-sized GaN substrates, named pore-assisted separation (PAS) method, where GaN substrate is separated at a porous layer formed electrochemically inside a seed GaN-template.