“…In addition, the AlN layer before GaN can not only reduce the Ga-melting back, but also can effectively improve the quality of GaN crystals [25]. The quality of (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) GaN grown by this method still depends sensitively on many parameters, such as trench width [26], growth temperature [27], V/III ratios, etc [28][29][30]. For example, semipolar (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) GaN can be grown on (113) Si in the V/III ratio range of 470-1730 [24,28,29,31,32], but there is a significant difference in the quality of the GaN.…”