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Photoluminescence Study on InGaN/GaN Quantum Well Structure Grown on (112̄0) Sapphire Substrate

An investigation of temperature-dependent photoluminescence is carried out on InGaN/GaN multiple-quantum-well (MQW) structures with 2.5 nm well thickness grown on (0001) and (112̄0) orientation sapphire substrates. Based on a band-tail model, the exciton localization effect is investigated with regard to the substrate orientation. On the (0001) sapphire substrate, the emission energy decreases monotonically with increasing temperature from 10 K to room temperature. However, on the (112̄0) sapphire substrate, the emission energy shows a temperature-induced blue shift at temperatures above 70 K, which is a typical characteristic of the occurrence of the exciton localization effect in an InGaN/GaN quantum well structure. Therefore, our result indicates that the exciton localization effect can be enhanced by growing InGaN/GaN MQW structures on (112̄0) sapphire substrates. Since the exciton localization effect is generally accepted to be advantageous for enhancing the emission quantum efficiency of the InGaN/GaN MQW, the results presented in this paper should be seriously considered.