I need to understand if Optical-gain peak, (Photoluminescence) PL peak and the Electroluminescence (EL) peak are they same or different. If they are the same/different what the corresponding conditions? Would be easier for me if bulk GaAs is used for the explanation (comparison at same temperature). Ultimately I would like to understand this for QW (say AlGaAs/GaAs). Any reference which explains this would be useful. Thanks.