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

• Growth temperature dependent critical thickness for phase separation.
• Growth of thick (≳1 μm) InGaN without phase separation.
• Initiation of phase separation in InGaN films.
• SIMS In/Ga intensity ratio profiles in InGaN films.

This paper reports phase separation in thick (~1 μm) 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 0.2 μm for a film grown at 750 °C, while it is more than 1 μm 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 0.2 μm 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.