Increasing laser excitation power induces large blue shift of the photoluminescence peak of quantum wells in gallium nitride

Abstract

It is experimentally demonstrated that, as the output power density of a nitrogen laser is increased from 10 to 1000 kW/cm², a peak in the photoluminescence spectrum of quantum wells (QWs) in GaN shifts by approximately 150 meV. This behavior cannot be interpreted within the framework of the ideal QW model. The observed phenomenon is theoretically explained by the presence of a “tail” in the localized density of states in the QW bandgap and by the filling of bands in the QW by nonequilibrium photogenerated charge carriers. A phenomenological expression for the density of states is proposed, which takes into account the tail in the localized density of states and provides qualitative agreement between theoretical and experimental spectra.