Investigating efficiency droop in InGaN/GaN quantum well structures using ultrafast time-resolved terahertz and photoluminescence spectroscopy

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• 作者：Aniela Dunn ; Ben F. Spencer ; Samantha J. O. Hardman ; Darren M. Graham ; Simon Hammersley ; Matthew J. Davies ; Phil Dawson ; Menno J. Kappers ; Rachel A. Oliver and Colin J. Humphreys
• 刊名：physica status solidi (c)
• 出版年：2016
• 出版时间：May 2016
• 年：2016
• 卷：13
• 期：5-6
• 页码：252-255
• 全文大小：447K
• ISSN：1610-1642a

文摘

The mechanisms governing efficiency droop in an In_0.18Ga_0.82N/GaN multiple quantum well structure were investigated using a combination of ultrafast time-resolved terahertz and photoluminescence spectroscopy. From excitation fluence dependent studies, a reduction in the room temperature photoluminescence efficiency to 3% of its maximum value was observed for an excitation fluence of 0.96 mJcm^-2. A correlation was found between the onset of efficiency droop and the emergence of a peak on the high-energy side of the quantum well emission with a 1/e decay time of 19.6 ps. These characteristics were attributed to the saturation of localised states and the population of higher energy delocalised states. Time-resolved studies revealed different scaling behaviours between the terahertz and photoluminescence decay dynamics, suggesting that the saturation of localised hole states may be playing a part in the onset of efficiency droop. (