Growth temperature dependent critical thickness for phase separation in thick (~1 μm) InxGa1−xN (x=0.2–0.4)

Abstract

This paper reports phase separation in thick (~1μm) MOVPE InxGa1−xN (x=0.2–0.4) films grown by MOVPE at 570–750°C on AlN/Si(111), α-Al2O3(0001) and GaN/α-Al2O3(0001) substrates. Phase separation occurs when InGaN thickness exceeds a critical value. Critical thickness for phase separation is markedly increased with decreasing growth temperature. It is around 0.2μm for a film grown at 750°C, while it is more than 1μm for that grown at 570°C. No substrate dependencies are found in critical thickness. The cross-sectional SEM views of phase-separated films grown at 650°C show that phase separation is initiated at parts far more than 0.2μm from the substrate and extended to the area near the substrate. SIMS analysis shows a possibility that phase separation is initiated at a part with relatively large In/Ga ratio fluctuations in InGaN films.