Impact of metalorganic vapor phase epitaxy growth conditions on compressive strain relaxation in polar III-nitride heterostructures

Abstract

A novel approach to estimating the critical thicknesses (CTs) of compressively strained III-nitride layers is suggested, based on a quasi-thermodynamic growth model and accounted for the effect of material decomposition during dislocation half-loop formation on the CT value. The approach provides good quantitative agreement with available data on CTs of MOVPE-grown InGaN/GaN and AlGaN/AlN epilayers. The extremely large CTs observed for high Al-content AlGaN alloys grown on bulk AlN substrates may be attributed, in particular, to the dominant AlGaN decomposition mechanism, producing group-III metallic liquid and gaseous nitrogen. The suggested approach may also be helpful for analysis of threading dislocation inclination in compressively strained layers and applicable to studying point defect formation in semiconductors and its dependence on growth conditions.