Reduced radiative currents from GaAs/InGaAs and AlGaAs/GaAs p-i-n quantum well devices

Calibrated electroluminescence spectra of GaAs/InGaAs and AlGaAs/GaAs single and double quantum well (QW) p-i-n devices, at various temperatures (200-300K) and applied biases (V-app = 0.8-1.5V), have been compared to theory to extract the quasi-Fermi level separation, Delta phi(f), in the QWs and where possible in the host material. Emission from the host material for the GaAs/InGaAs cell is well fitted with Delta phi(f) = V-app at all biases and temperatures. In contrast, emission from the QW in both GaAs/InGaAs and AlGaAs/GaAs cases requires a value of Delta phi(f) which is a few tens of meV less than V-app. We attribute the variations in Delta phi(f) to irreversible thermally assisted escape from the QWs and detail some preliminary results from double QW samples.