Band tailing and the spontaneous spectra of compensated epitaxial GaAs laser junctions

The spectra of the spontaneous emission from GaAs laser diodes fabricated by vapor-phase epitaxy and containing a high degree of compensation in the p-type side of the junction are, in many respects, similar to those previously reported for the cathodoluminescence of homogeneous p-type material. The temperature dependence of the spectra of these diodes supports a model where the emission is attributed to radiative transitions between a narrow band of states near the conduction-band edge and an exponential distribution of states extending the valence band into the forbidden gap. An increase in temperature then results in an increase or a decrease in the radiative power output depending on the position of the quasi-Fermi level for electrons relative to the above narrow band of states and a distribution of nonradiative levels below it.