Effects of carrier gas ratio and growth temperature on MOVPE growth of AlN

Abstract

AbstractThe strong demand for high‐efficiency light‐emitting diodes in the deep‐ultraviolet region and for sensors has led to renewed interest in the growth of high‐quality AlN. However, the growth of high‐quality AlN is extremely difficult owing to the low surface migration rate of Al adatoms. In this study, the effects of the carrier gas ratio and growth temperature on the growth rate of AlN are examined with the aim of optimizing the growth conditions of high‐temperature AlN. AlN epilayers were grown on sapphire substrates by metal‐organic vapor phase epitaxy (MOVPE) at a growth temperature of 1430 °C with a medium‐temperature AlN layer grown at 1100 °C. A combination of H2 and N2 was used as the carrier gas in the growth of AlN, and the ratio of H2 to N2 in the carrier gas was changed to examine its effect on the growth of AlN. Under all growth conditions, crack‐free and smooth surfaces at the atomic level with an extremely small tilt were obtained. The growth rate decreased with increasing growth temperature and ratio of H2 in the carrier gas. This suggests that the high temperature and the H2 carrier gas inhibit the adsorption of atoms. Also, with increasing ratio of N2 in the carrier gas, the radius of curvature of the AlN layer increased and the compressive strain decreased. The reduction of compressive strain and increase in curvature of the AlN layer were due to an increase in the number of dislocations. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)