Longitudinal-optical phonon broadening due to nitrogen atom incorporation in InGaAsN/GaAs quantum wells

We present a study of the optical properties of double quantum wells of In0.3Ga0.7As1-xNx/GaAs. The nitrogen composition, x, ties between 2 10(-3) and 9.5 10(-3). Temperature dependence of time integrated photoluminescence (PL) and time-resolved PL have been investigated. The temperature dependences of the PL energy and the linewidth are correlated, and they show that the carriers are localised at low temperature. Consistently the energy dependence of decay time across the PL line is analysed in terms of mobility edge. The carrier localisation at low temperature is due to alloy disorder in the wells which induces potential fluctuations. The PL linewidth increases with temperature. This linewidth is also strongly increased by the increase of the N composition. We attribute this behaviour to an enhanced coupling of the carriers with LO phonons. We deduce from these results that N incorporation increases the polar character of the III-V compound.