Influence of growth stress on the surface morphology of N-polar GaN films grown on vicinal C-face SiC substrates

In-situ stress measurements were used to monitor the growth of N-polar GaN films on vicinal C-face SiC substrates using a two-step temperature process. A reduction in compressive stress in the N-polar GaN and a corresponding decrease in surface roughness were observed as the initial growth temperature was reduced from 1000 °C to 900 °C. The results suggest that compressive stress in N-polar GaN promotes step bunching and macroscale roughness in films grown on vicinal substrates. The reduction in compressive stress is proposed to originate from tensile thermal stress induced by the temperature change in the two-step process.