Influence of Ga/N ratio on morphology, vacancies, and electrical transport in GaN grown by molecular beam epitaxy at high temperature

The effect of Ga/N flux ratio on surface morphology, incorporation of point defects and electrical transport properties of GaN films grown by plasma-assisted molecular beam epitaxy in a recently developed high-temperature growth regime was investigated. The homoepitaxial (0001) GaN films grown at $∼780–790°C$ showed smoothest morphologies near the cross-over between N-rich and Ga-rich growth $(0.75<Ga/N<1.1)$ contrasting previous observations for low-temperature growth. The higher-quality growth near $Ga/N∼1$ resulted from lower thermal decomposition rates and was corroborated by slightly lower Ga vacancy concentrations $[VGa]$⁠, lower unintentional oxygen incorporation, and improved electron mobilities. The consistently low $[VGa]$⁠, i.e., $∼1016cm−3$ for all films attribute further to the significant benefits of the high-temperature growth regime.