Studies on Carrier Recombination in GaN/AlN Quantum Dots in Nanowires with a Core-Shell Structure.

Jun Deng,Lai Wang,Changzheng Sun,Zhibiao Hao,Yi Luo,Wei Zhao,Xihui Liang,Hongtao Li,Jian Wang,Junjun Wang,Yanjun Han,Bing Xiong,Jiadong Yu

doi:10.3390/nano10112299

Abstract

GaN quantum dots embedded in nanowires have attracted much attention due to their superior optical properties. However, due to the large surface-to-volume ratio of the nanowire, the impacts of surface states are the primary issue responsible for the degradation of internal quantum efficiency (IQE) in heterostructured dot-in-nanowires. In this paper, we investigate the carrier recombination mechanism of GaN/AlN dot-in-nanowires with an in situ grown AlN shell structure. Ultraviolet photoelectron spectroscopy (UPS) measurements were performed to describe the band bending effect on samples with different shell thicknesses. Temperature-dependent photoluminescence (TDPL) data support that increasing the AlN shell thickness is an efficient way to improve internal quantum efficiency. Detailed carrier dynamics was analyzed and combined with time-resolved photoluminescence (TRPL). The experimental data are consistent with our physical model that the AlN shell can effectively flatten the band bending near the surface and isolate the surface non-radiative recombination center. Our systematic research on GaN/AlN quantum dots in nanowires with a core–shell structure may significantly advance the development of a broad range of nanowire-based optoelectronic devices.

Highlights

Over the past decade, III-nitride semiconductor quantum dots in nanowires have attracted much attention due to their potential applications in solid-state lighting [1,2,3,4], photochemical sensing [5], and quantum cryptography [6]
Several groups have reported self-assembled III-nitride quantum dots in nanowires grown by molecular beam epitaxy (MBE) [7,8,9,10]
III-nitride quantum disks embedded in nanowires demonstrate superior optical properties, such as stronger quantum confinement [6,11], smaller Auger recombination coefficient [12], and suppressed quantum-confined Stark effect (QCSE) [1]

Summary

Introduction

III-nitride semiconductor quantum dots in nanowires have attracted much attention due to their potential applications in solid-state lighting [1,2,3,4], photochemical sensing [5], and quantum cryptography [6]. We investigated the carrier recombination mechanism of GaN/AlN quantum dots in nanowires grown on silicon substrates using MBE. By precisely adjusting the Al flux, GaN/AlN quantum dots in nanowires with different AlN shell thicknesses were obtained.

Results

Conclusion