Thermally detected optical absorption and photoluminescence studies of InGaAsN/GaAs quantum wells

Both thermally detected optical absorption and photoluminescence as a function of temperature are used to investigate the electronic states of InGaAsN/GaAs quantum wells grown by molecular beam epitaxy. The band structure of InGaAsN is first described within the two-band model, assuming that nitrogen only affects the conduction band through the interaction between the localised nitrogen level and the host matrix conduction band. Taking advantage of the accurate knowledge of strained InGaAs/GaAs layers, a simple model allows the calculation of the energy levels in InGaAsN/GaAs quantum wells. Furthermore, the labelled ten-band k.p model is used to derive the strained conduction band offset. The calculations of transition energies in the wells compare favourably with experimental results. From photoluminescence experiments at different temperatures, the ionisation of impurities together with the transition between localisation-delocalisation of the carriers in the well are evidenced.