Homogeneous broadening and k-vector conservation in direct bandgap transitions

Abstract

k-vector conservation is studied in direct bandgap optical transitions by examining edge emitted photoluminescent and electroluminescent spectra. Inhomogeneously and homogeneously broadened spectra are identified in tensile strained, single quantum well, broad stripe laser diode structures. In low excitation conditions, the molecular beam epitaxy (MBE) deposited test structures showed Urbach-tail like inhomogeneous broadening with small Urbach parameter values, typical for high quality materials. At high excitation conditions, significant deviations from Lorentzian line shape were observed and concluded to arise from k-vector conservation within the line broadening process.