Linearly polarized photoluminescence of InGaN quantum disks embedded in GaN nanorods

Youngsin Park,Luke Nuttall,Christopher C S Chan,Nammee Kim,Robert A Taylor,Hyunsik Im,Tim J Puchtler,Yongcheol Jo

doi:10.1038/s41598-018-26642-8

Abstract

We have investigated the emission from InGaN/GaN quantum disks grown on the tip of GaN nanorods. The emission at 3.21 eV from the InGaN quantum disk doesn’t show a Stark shift, and it is linearly polarized when excited perpendicular to the growth direction. The degree of linear polarization is about 39.3% due to the anisotropy of the nanostructures. In order to characterize a single nanostructure, the quantum disks were dispersed on a SiO2 substrate patterned with a metal reference grid. By rotating the excitation polarization angle from parallel to perpendicular relative to the nanorods, the variation of overall PL for the 3.21 eV peak was recorded and it clearly showed the degree of linear polarization (DLP) of 51.5%.

Highlights

Wurtzite GaN and its family of compounds such as InN, InGaN etc. have a strong piezoelectric field along the crystal c-axis[1], which causes a quantum confined Stark effect (QCSE)
Whilst the PL intensities of the D°X near 3.47 eV and I1 near 3.41 eV are independent on the polarizer angle, that of the quantum disks (QDisk) related emission near 3.21 eV shows a clear sinusoidal variation
In order to investigate the polarization of the individual nanorod structure, the QDisks grown on the GaN nanorods with a diameter of 150 nm were mechanically detached from the as grown substrate into an acetone solution by a brush and the solution was spread over the metal marked SiO2 wafer (Supporting information S3)

Summary

Introduction

Wurtzite GaN and its family of compounds such as InN, InGaN etc. have a strong piezoelectric field along the crystal c-axis[1], which causes a quantum confined Stark effect (QCSE). Have a strong piezoelectric field along the crystal c-axis[1], which causes a quantum confined Stark effect (QCSE). This can induce harmful effects to device performance due to the shift of the emission energy and the separation of the electron-hole wavefunction in space. Photon antibunching and linearly polarized emission were demonstrated from InGaN/GaN quantum dots (QDs) and attributed to the valence-band mixing by the lateral anisotropy of the wurtzite group-III nitrides[5,6,7]. The PL peak around 3.21 eV originating from the InGaN QDisks doesn’t show the Stark shift and polarized emission with a degree of linear polarization (DLP) of 39.3% was observed when the nanorods were excited orthogonally to their growth axis due to crystal anisotropy. In order to characterize a single nanostructure, the QDisks were spread on a reference marked SiO2 substrate

Methods

Results

Conclusion