Free charges versus excitons

photoluminescence investigation of InGaN/GaN multiple quantum well nanorods and their planar counterparts

Weijian Chen, Xiaoming Wen, Jianfeng Yang, Michael Latzel, Robert Patterson, Shujuan Huang, Santosh Shrestha, Baohua Jia, David J. Moss, Silke Christiansen, Gavin Conibeer*

*Corresponding author for this work

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

InGaN/GaN multiple quantum well (MQW) nanorods have demonstrated significantly improved optical and electronic properties compared to their planar counterparts. However, the exact nature of the processes whereby nanorod structures impact the optical properties of quantum wells is not well understood, even though a variety of mechanisms have been proposed. We performed nanoscale spatially resolved, steady-state, and time-resolved photoluminescence (PL) experiments confirming that photoexcited electrons and holes are strongly bound by Coulomb interactions (i.e., excitons) in planar MQWs due to the large exciton binding energy in InGaN quantum wells. In contrast, free electron-hole recombination becomes the dominant mechanism in nanorods, which is ascribed to efficient exciton dissociation. The nanorod sidewall provides an effective pathway for exciton dissociation that significantly improves the optical performance of InGaN/GaN MQWs. We also confirm that surface treatment of nanorod sidewalls has an impact on exciton dissociation. Our results provide new insights into excitonic and charge carrier dynamics of quantum confined materials as well as the influence of surface states.

Original languageEnglish
Pages (from-to)5358-5365
Number of pages8
JournalNanoscale
Volume10
Issue number11
DOIs
Publication statusPublished - 21 Mar 2018
Externally publishedYes

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