Effect of growth temperature and Si doping on the microstructure of GaN thin films grown on high temperature GaN

Effects on structural characteristics of growth temperature and Si doping in GaN thin films grown on high temperature GaN were investigated. The GaN/GaN homojunction structure was grown via MOCVD at intermediate temperature (IT, 840 °C) with various Si doping concentrations. V-shaped pits are observed on the surface of the undoped GaN grown at IT by AFM morphology analysis. TEM two beam images show that only screw- and mixed-type components of dislocations contribute to pit formation. Moderate Si doping reduces the pit density, but over-doping of Si deteriorates the IT-GaN property by forming pits again. Not all pits are related with threading dislocations but some of them are observed in the dislocation free area of high Si-doped GaN.