Strong potential profile fluctuations and effective localization process in InGaN∕GaN multiple quantum wells grown on {10-1m} faceted surface GaN template

Abstract

Cathodoluminescence (CL) and time-resolved photoluminescence (TRPL) spectroscopy were used to investigate the relation between the surface morphology and emission efficiency in 10× InGaN(3nm)∕GaN(4nm) quantum wells (QWs) deposited by plasma-assisted molecular beam epitaxy (MBE). For this study, two QWs with peak emission around 405nm but grown on different surface morphologies have been investigated. A strong increase in the emission efficiency was observed in the QWs grown on {10-1m} faceted surface GaN template (m>2) as compared to those grown on an atomically smooth template. CL mapping and temperature-dependent PL studies revealed that the QWs grown on the faceted surface GaN epilayer exhibit much stronger in-plane indium content fluctuations and larger width PL peak in the temperature range of 8–300K. We found that the use of {10-1m} faceted surface GaN template resulted in strong potential profile fluctuations (PPFs) inducing different localization centers at different energy levels. We found that the deeper the corresponding fluctuation of the energy level, the weaker the decrease of the PL intensity with increasing temperature, the higher the PL decay time (τPL) in the whole temperature range and the slower the collapse of τPL. Our results demonstrate that the use of {10-1m} faceted surface morphology GaN template is an amplifying process of the PPFs which favors a regime dominated by the recombination of localized carriers.