Influence of an embedded low-temperature AlN strain relaxation layer on the strain states and the buffer characteristics of GaN films grown on (110) Si substrates by using ammonia molecular beam epitaxy

Abstract

The effect of a low-temperature AlN strain relaxation layer on the strain state and the leakage characteristics of GaN buffer layers grown on (110) Si substrates by using ammonia molecular beam epitaxy has been investigated. Excess charge accumulation at the position of LT-AlN strain relaxation layer is found to result in a leakage current through the GaN buffer layer that is a few orders of magnitude higher than through the GaN buffer layer without the LT-AlN strain relaxation layer. An approach to grade the Al composition of the LT-AlN layer reduces the detrimental leakage current induced by the use of the LT-AlN layer while keeping the compressive strain state of the GaN buffer layer on a (110) Si substrate. A complete understanding of charge formation in the strain relaxation layer in the GaN buffer layers on (110) Si substrates is required to accomplish a crack-free and dopant-free GaN buffer layers for use in high-power/high-frequency electronic devices.