Effects of low temperature buffer layer treatments on the growth of high quality ZnO films

ZnO films were grown on sapphire substrates by radical source molecular beam epitaxy (RS-MBE). ZnO low temperature buffer layers were subjected to various treatments. High quality ZnO films were obtained by vacuum annealing plus nitrogen doping of the buffer layer. The carrier concentration of the ZnO film fabricated using this buffer layer was 7.5 x 10(16) cm(-3) with a mobility of 132 cm(2)/V see at RT. Temperature dependent Hall measurements showed implied the existence of degenerate (untreated) buffer layers. Using a nitrogen-doped buffer layer to reduce the influence of the degenerate layer, a donor energy of 110 meV was estimated from temperature dependent Hall measurements. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.