Transport and optical properties of a GaAs/AlAs superlattice-like double-barrier diode were studied by continuous-wave photoluminescence spectroscopy. An enhancement of the quantum-well photoluminescence intensity with increasing temperatures is reported in biased diodes, which is related to transport properties, disappearing at zero-applied voltage. The anomalous observed behavior can be explained in terms of the temperature-dependent transport properties of the minority carriers (holes) in the collector spacer layer, which limits the supply of holes available for tunneling.