Polarity control of GaN thin films grown by metalorganic vapor phase epitaxy

Abstract

Control of the polarity of GaN thin films grown on c-plane sapphire by low-pressure metalorganic vapor phase epitaxy has been achieved. Growth of either polarity was realized by identifying and selecting appropriate substrate pre-treatments and AlN LT-buffer growth conditions. N-face (–c) GaN films were only obtained by pre-nitridation of the sapphire substrate after a H2 anneal. Smooth films of each type of polarity were obtained by using N2 as a transport and dilution gas and a V/III ratio of less than 500. The same growth rate of 1.2 µm/h was observed for both types of polarities under the same growth conditions. Further analysis of the growth conditions demonstrated that by using N2 as the dilution gas the transport was mass-transfer limited. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)