The nature of optical transitions in Ga0.64In0.36As1−xNx/GaAs single quantum wells with low nitrogen content (x≤0.008)

Ga0.64In0.36As1−xNx/GaAs single quantum wells (SQWs) with low nitrogen content have been investigated by both photoluminescence (PL) and photoreflectance (PR) at low and room temperatures. A huge broadening of the PR features has been observed at low temperature and a decrease in this broadening with the temperature increase was detected. This effect and the nature of the optical transitions observed in absorption and emission can be explained using a model which assumes band gap variation due to different nitrogen nearest-neighbour environments (different configurations). In the framework of this model, the large Stokes shift observed for quantum wells (QWs) with smooth interfaces is explained as originating from the potential fluctuations of conduction band edge in the QW layer.