STUDY OF LONG TIME-SCALE PHOTOLUMINESCENCE DYNAMICS OF GAN/INGAN QUANTUM WELLS AND COMPARISON WITH SAMPLES GROWN ON ELOG-GAN

摘要

Many researches on In_xGa_((1-x))N systems are focused on their optical characteristics, and in particular on their behaviour in very small time scale range. Conversely, in this report we studied optical phenomena that have long-range time constants. In particular, we studied samples where a thin InGaN/GaN interface defines a single quantum well (SQW) structure in the crystal. Tiny fluctuation of the Indium concentration in the SQW induces localized regions of high Photoluminescence (PL) emission. We established conditions by which temporal instabilities in the PL optical signal were detected and characterized. In this study we will present details on these measurements, in particular we will show how locally indium-rich centers seem to be directly involved in the blinking phenomena. We will report too on the dependence of the temporal behaviour with large-scale (bulk) Indium concentration, and we will show how an epitaxially laterally overgrown GaN (ELOG) substrate influence the PL temporal instabilities.