Localization effect in green light emitting InGaN/GaN multiple quantum wells with varying well thickness

Green light emitting InGaN/GaN multiple-quantum-well (MQW) structures with varying well thickness are grown via metal-organic chemical vapor deposition (MOCVD). The localization effect in these samples is studied by means of temperature-dependent photoluminescence (PL) measurements. The S-shape shift of PL peak energy with increasing temperature is observed, from which the extent of localization effect is determined quantitatively by using a band-tail model. It is found that the composition-related deep localization states dominate the light emission in thin-well MQWs, while in thick-well MQWs the shallow localization states induced by the fluctuations of InGaN well thickness dominate the luminescence efficiency. It is considered that in the thinner wells the improved emitting efficiency may partially originate from the stronger localization effect.