Recent development of InN RF-MBE growth and its structural and property characterization

This paper describes studies on high-quality InN growth on sapphire by RF-MBE. Critical procedures to obtain high-quality InN films include (1) nitridation process of sapphire substrates prior to growth, (2) two-step growth method including the growth of a low-temperature InN-buffer layer, (3) precise control of V/III ratio and (4) selection of optimum growth temperature. Detailed structural characterizations by XRD, TEM, Raman scattering and EXAFS indicate that InN films have ideal hexagonal wurtzite structure. Further studies using TEM indicate that the grown InN has an ABAB... stacking sequence without inclusion of the cubic phase. However, threading dislocations with a high density of more than 2x10(10) cm(-2) and a distinct columnar domain structure are observed. FWHMs of omega-20 mode XRD and E-2(high)phonon-mode of Raman scattering are as small as 28.9 arcsec and 3.2 cm(-1), respectively. True band gap energy of InN is also discussed based on optical characterization results obtained from well-characterized hexagonal InN and InGaN grown in this study. Single-crystalline InN films are obtained on Si substrates by a brief nitridation of the Si substrates. Significant improvement of InN crystal quality on Si substrates by the insertion of an AlN buffer layer is also demonstrated. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.