Thickness dependence of temperature-induced emission mechanism in InGaN/AlGaN short-period superlattices

An analysis of temperature-dependent photoluminescence (PL) spectra for a series of InGaN/AlGaN short-period superlattices (SP-SLs) with different well and barrier thickness is presented. A quantitative model, based on Gaussian-like function of localized electronic states, to fit the temperature-dependent emission peak energy gives good fits over an extended temperature range for all samples. It is found that, among all parameters in the model, the degree of broadening of the Gaussian distribution is strongly dependent of the structural parameters of SP-SLs and determines the anomalous "S-shape" behavior of the temperature-dependent emission energy. In thin well and barrier samples with higher broadening parameter, the temperature-dependence of emission energy is different from those of typical "S-shape" behavior, which is characterized by the bigger red-shift with no blue shift in the temperature range used. The depth of localization, E-a-E-o, is smaller than the corresponding activation energy obtained from the thermal quenching of the PL intensity, thus, indicating that the thermal quenching activation energy and the localization due to band-gap fluctuation most likely have different origins. We demonstrate that, in the InGaN/AlGaN SP-SLs, the interface characteristics also contributes to the temperature-induced PL emission shift as much as the compositional fluctuation does. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4746744]