Crack-free GaN substrates grown by the Na-flux method with a sapphire dissolution technique

摘要

GaN wafers are generally fabricated by separating a foreign substrate from a GaN layer using thermal stress; however, thermal stress also leads to the cracking of the GaN layer. In this study, we first succeeded in dissolving a sapphire substrate just after Na-flux growth by successively changing the flux content for GaN growth (Ga-Na-C) to that for dissolving sapphire (Ga-Na-C-Li) at the considered growth temperature. Hence, no thermal stress was induced in the grown GaN crystals, resulting in a crack-free GaN substrate. We concluded that this process is a good candidate technique for supplying free-standing GaN substrates. (C) 2016 The Japan Society of Applied Physics