In this study, GaN layers on sapphire were grown by hydride vapor phase epitaxy (HVPE). And free standing (FS) GaN layers were obtained after laser lift off (LLO) process. We controlled growth temperature to minimized bow of the FS-GaN after LLO process. Target thickness of GaN epilayers were over 300 mu m. GaN templates showed strong convex bowing at room temperature and the bow values showed any particular relation with growth temperature. But bows of FS-GaN substrates after LLO treatment showed mainly concave mode and those decreased according to reducing the growth temperature from 1010 degrees C to 1000 degrees C We show that reduction of bows in FS-GaN can be controlled by the growth condition of HVPE process.

Keywords: GaN substrate; Free standing GaN; HVPE and Bow