MBE Growth and Characterization of Device-Quality Thick InN Epilayers; Comparison between N-polarity and In-polarity Growth Processes

Epitaxy of InN films with N-polarity and In-polarity was investigated by RF-MBE with several in-situ monitoring/controlling systems. It was found that the epitaxy temperature for N-polarity growth could be as high as 600 °C and this was about 100 deg higher than that for In-polarity case. This temperature difference in two polarities drastically affected not only the growth behaviors but also the properties of InN epilayers, i.e. N-polarity growth was preferable in both view-points. The step-flow-like surface morphology was achieved for the InN films grown with N-polarity at 580 °C. The FWHMs of X-ray rocking curves for InN (002) and (102) of 5-8 µm-thick InN films grown in N-polarity were about 200-350 and 650-950 arcsec, respectively. The highest Hall mobility was above 2000 cm2/Vs with a background carrier concentration of 1-2×1018 cm−3 at room temperature. For both polarity films, N-rich condition was necessary for the stable InN growth to obtain 5-8 µm-thick InN films.