Determination of photoluminescence mechanism in InGaN quantum wells

We report on the unambiguous experimental determination of the photoluminescence mechanism in a set of In0.25Ga0.75N quantum wells. Instead of studying the photoluminescence for different In contents, we have investigated it as a function of the quantum well width in combination with a similar study performed on GaN quantum wells. In this way, we show that the photoluminescence is not coming from quantum dots or very localized states in the quantum well, but from the quantum well itself under the influence of a piezoelectric field induced by strain. The previously reported abnormal photoluminescence shifts and temperature dependencies can thus be explained.