Halide vapor phase epitaxy of thick GaN films on ScAlMgO4substrates and their self-separation for fabricating freestanding wafers

Halide vapor phase epitaxy of thick GaN films was demonstrated on ScAlMgO4(SCAM) substrates, and their self-separation was achieved. The 320-µm-thick GaN film was self-separated from the SCAM substrate during the cooling process after the growth. This separation phenomenon occurred because of both the c-plane cleavability of SCAM and the difference in the thermal-expansion coefficients between GaN and SCAM. The dark-spot densities for the GaN films on the SCAM substrates were approximately 30% lower than those on sapphire substrates. These results indicate that SCAM substrates are promising for fabricating a high-quality freestanding GaN wafer at a low cost.