Optical properties of InGaN alloys: an unsolved mystery

Abstract

The high efficiency of luminescence from InGaN has made possible the widespread recent developments in blue-green semiconductor optoelectronics. Localisation of excitations, whether by composition fluctuations or self-formed quantum dots, appears to tilt the balance in favour of radiative recombination, despite the presence of huge densities of extended defects found in ‘device-grade ’material. What is not clear at the present stage is the relationship between the composition and structure; what exactly is responsible for optical effects in this material? Why does In incorporation markedly increase the luminescence efficiency? Despite much research regarding this material, we are still confronted by a mystery when considering the origin of luminescence from InGaN. In this lecture, some of the key optical and structural properties of InGaN alloys were presented, and some of the remaining open questions were highlighted.