Electric-field dependence of luminescence spectra of (In,Ga)N/GaN LEDs containing quantum wells

Abstract

Both the luminescence intensity and the optical transition energy of single and multiple (In,Ga)N/GaN quantum wells (QW) embedded in the depletion region of a p-n junction vary strongly with the applied bias voltage and with the excitation density. The electric-field dependence of the cathodoluminescence (CL) intensity is governed by the competition between carrier drift within the depletion region and carrier capture by the QWs. A gradual screening of the p-n junction field with increasing excitation density causes a strongly nonlinear CL response. The electric-field dependence of the optical transition energy is governed by a gradual compensation of the polarization field of the QWs by the p-n junction field as well as by filling of band tail states of localized excitons. While the CL spectra of the QWs reflect radiative recombination of both free and localized excitons, electroluminescence spectra are dominated by the recombination of localized excitons.