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 (200-300 K) and biases (0.8-1.5 V), have been compared to theory to extract the quasi-Fermi level separation, /spl Delta//spl phi//sub 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 /spl Delta//spl phi//sub f/=V/sub app/ at all biases and temperatures. In contrast, emission from the QW in both GaAs/InGaAs and AlGaAs/GaAs cases requires a value of /spl Delta//spl phi//sub f/ which is a few tens of meV less than V/sub app/. We attribute the variations in /spl Delta//spl phi//sub f/ to irreversible thermally assisted escape from the QWs and detail some preliminary results from double QW samples.