The c-axis and a-axis orientations in InN grown directly on (0001) sapphire substrate by rf-MBE

InN films were grown on (0001) sapphire substrates by radio-frequency plasma-excited molecular beam epitaxy. Even without the initial growth processing, which includes substrate nitridation and buffer layer deposition, the c-axis orientation in InN films was well controlled by increasing the growth temperature but keeping the temperature below the InN dissociation temperature. However, without initial growth processing, the a-axis orientation in InN films tended to have various rotation domains within the c-plane. Hence, the initial growth processes of substrate nitridation and buffer layer deposition were useful and effective ways to control the rotation domains.