Carrier density dependence of polarization switching characteristics of light emission in deep-ultraviolet AlGaN/AlN quantum well structures

Abstract

The carrier density dependence of the polarization switching characteristics of the light emission in deep-ultraviolet AlGaN/AlN quantum well structures was investigated using the multiband effective-mass theory and non-Markovian model. The critical Al composition from transverse electric (TE) to transverse-magnetic (TM) polarization decreases gradually with increasing carrier density. This can be explained by the fact that matrix elements for TM-polarization above the band-edge (k(parallel to) = 0) is much larger than those for TE-polarization. That is, the light emission for TM-polarization becomes larger than that for TE-polarization at higher carrier density because carriers will occupy higher states above k(parallel to) = 0 in the conduction and valence bands. As a result, the critical Al composition is reduced with increasing carrier density. Also, the critical Al composition is observed to decrease with increasing well width. (C) 2013 AIP Publishing LLC.