GaN substrate and GaN homo-epitaxy for LEDs: Progress and challenges<xref ref-type="fn" rid="cpb150941fn1">*</xref>

GaN substrate and GaN homo-epitaxy for LEDs: Progress and challenges*

Wu Jie-Jun, Wang Kun, Yu Tong-Jun†, Zhang Guo-Yi

(a) Growth procedure in an order of the numbers for the sapphire pre-h-treatment method; (b) Delamination of self-separation caused by the large thermal mismatch stress and the edge shear stress; (c) Self-separated GaN layer on sapphire substrate; (d) 2-inch free-standing GaN substrate; (e) sapphire substrate with non-mirror surface on top after GaN layer removal, and (e) the CL spectrum from the sapphire surface after separation, strong GaN peak indicating GaN film remained as the proof of part of separation path inside the GaN layer.^{[ 40 ]}