Field dependence of barrier heights and luminescence properties in polar and nonpolar InGaN/GaN single quantum wells

The external field dependence of barrier heights and the internal field dependence of luminescence properties in InxGa1-xN/GaN single quantum wells (SQWs) with polar (x=0.13) and nonpolar (x=0.15) orientations were investigated. The conduction band offset of a SQW was characterized by using deep level transient spectroscopy. At a reverse bias of -3 V, the barrier height of the nonpolar SQW was estimated to be 0.42 eV, which is smaller than the 0.60 eV seen in the polar SQW due to the absence of internal fields along the nonpolar direction. Both samples showed a redshift of barrier heights with increasing reverse bias. The carrier recombination affected by carrier localization, quantum-confined Stark effect, and Varshni's shift was analyzed through temperature-dependent photoluminescence. Numerical simulations of the barrier heights and internal fields showed good agreement with experimental results.