GaN substrate and GaN homo-epitaxy for LEDs: Progress and challenges*
Wu Jie-Jun, Wang Kun, Yu Tong-Jun†, Zhang Guo-Yi
       
(a) Schematic picture of the self-separation mechanism of the surface pre-treatment method, in which the special buffer will decompose during the HT-growth process leading to self-separation; (b) Self-separated system of GaN layer on the left sapphire substrate; (c) Large size of free-standing GaN substrate with some dark growth edge, indicating separation took place during the HT-growth process; (d) the left sapphire substrate with mirror surface, the insert showed the relatively CL spectrum without GaN peak, indicating there was no GaN left on the removed sapphire and separation took place at the interface.