Towards fabrication of In-polar InN films and InN/GaN MQWs

In-polarity InN films were grown by radio frequency plasma-assisted molecular-beam epitaxy and their structural properties as a function of III/V beam-flux ratio were investigated. It was found that the window for the surface stoichiometry to achieve high quality InN films was very narrow; only 11% change in In beam-equivalent pressure drastically affected surface morphology and structural property. This is because the upper-limited growth temperature of the In-polarity growth is as low as about 500 C. Under the growth condition around the unity stoichiometry, a step-flow-like surface with a 2 mono-layer step height was obtained in the In-polarity growth. Best values for the measurements of structural and electrical properties were as follows; full width at half maximum of X-ray rocking curves were 645 arcsec and 1425 arcsec for (0002) and (10-12) reflections, respectively and the electron concentration and mobility were 1.3 x 1018 cm-3 and 1650 cm2/V s, respectively. Furthermore, we tried to fabricate In-polarity InN/GaN multi-quantum wells with a 1 mono-layer InN well thickness. A result of X-ray 2θ-ω scan showed clearly satellite peaks up to 2nd order and fringe peaks, which indicates that a fine periodic structure is achieved in the In-polarity MQWs. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)