High quality InAlN/GaN heterostructures grown on sapphire by pulsed metal organic chemical vapor deposition

摘要

High quality InAlN/GaN heterostructures are successfully grown on the (0 0 0 1) sapphire substrate by pulsed metal organic chemical vapor deposition. The InAlN barrier layer with an indium composition of 17% is observed to be nearly lattice matched to GaN layer, and a smooth surface morphology can be obtained with root mean square roughness of 0.3 nm and without indium droplets and phase separation. The 50 mm InAlN/GaN heterostructure wafer exhibits a mobility of 1402 cm~2/V s with a sheet carrier density of2.01 × 10~(13) cm~(-2),and a low average sheet resistance of 234 Ω/cm~2 with a sheet resistance nonuniformity of 1.22%. Compared with the conventional continual growth method, PMOCVD reduces the growth temperature of the InAIN layer and the Al related prereaction in the gas phase, and consequently enhances the surface migration, and improves the crystallization quality. Furthermore, indium concentration of InAIN layer can be controlled by adjusting the pulse time ratio of TMIn to TMAl in a unit cycle, the growth temperature and pressure, as well as the InAlN layer thickness by the number of unit cycle repeats.