Contactless electroreflectance of GaInN/AlInN multi quantum wells: The issue of broadening of optical transitions

Contactless electroreflectance (CER) has been applied to investigate the energy and broadening of the fundamental transition for GaInN/AlInN multi quantum wells (MQWs) with the width varies from 1.3 to 1.8 nm. It has been found that the broadening of GaInN bulk-like transition equals ∼280 meV and increases significantly going to GaInN quantum wells (QWs). In order to explain experimental data, a simple theoretical analysis has been performed. It has been shown that the observed variation of broadening for the fundamental transition is associated with the QW width fluctuations. In addition, it has been estimated that the maximal width fluctuations in these MQWs equal ∼2 ML (∼30% of the QW width). Such a significant QW width fluctuations are attributed to the incorporation of indium atoms into this material system.