State-of-the-art and prospects for intense red radiation from core\u2013shell InGaN/GaN nanorods

Evgenii A Evropeitsev,Hiroshi Amano,Ilya A Eliseyev,Tatiana V Shubina,Alexander N Smirnov,Yoann Robin,Dmitrii R Kazanov,Shugo Nitta,Alexey A Toropov,Valery Yu Davydov

doi:10.1038/s41598-020-76042-0

Evgenii A Evropeitsev, Hiroshi Amano + Show 8 more

Open Access

https://doi.org/10.1038/s41598-020-76042-0

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Journal: Scientific Reports	Publication Date: Nov 4, 2020
Citations: 11	License type: open-access

Affiliation: Nagoya University, Ioffe Institute

Abstract

Core–shell nanorods (NRs) with InGaN/GaN quantum wells (QWs) are promising for monolithic white light-emitting diodes and multi-color displays. Such applications, however, are still a challenge because intensity of the red band is too weak compared with blue and green. To clarify this problem, we measured photoluminescence of different NRs, depending on power and temperature, as well as with time resolution. These studies have shown that dominant emission bands come from nonpolar and semipolar QWs, while a broad yellow-red band arises mainly from defects in the GaN core. An emission from polar QWs located at the NR tip is indistinguishable against the background of defect-related luminescence. Our calculations of electromagnetic field distribution inside the NRs show a low density of photon states at the tip, which additionally suppresses the radiation of polar QWs. We propose placing polar QWs inside a cylindrical part of the core, where the density of photon states is higher and the well area is much larger. Such a hybrid design, in which the excess of blue radiation from shell QWs is converted to red radiation in core wells, can help solve the urgent problem of red light for many applications of NRs.

Highlights

Core–shell nanorods (NRs), which comprise InGaN quantum wells (QWs) in a shell deposited over a GaN core, are among the most promising objects of modern n anophotonics[1]
Each set includes three samples which differ by In composition in QWs that is realized by the variation of the growth temperature, Tgr
The presence of a built-in electrostatic field in polar and semipolar QWs leads to spatial separation of electrons and holes

Summary

Introduction

Core–shell nanorods (NRs), which comprise InGaN quantum wells (QWs) in a shell deposited over a GaN core, are among the most promising objects of modern n anophotonics[1]. The blue light emitted from an electrically pumped active region was partially converted into yellow-red photoluminescence (PL) by the QWs of different widths and compositions. These QWs, situated outside the active region, were pumped only o ptically[11,12,13,14,15]. Semipolar, and nonpolar QWs, formed simultaneously, can emit in the red, green, and UV-blue regions, respectively[3,26] The advantages of such three-dimensional (3D) structures over planar ones are numerous: low dislocation density, use of nonpolar planes, large effective surface area, and high light extraction efficiency[1]. Important advantages of the NRs such as dislocation filtration and large effective area can be lost and the IQE will fall[29]

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