Investigation of a Separated Short-Wavelength Peak in InGaN Red Light-Emitting Diodes

Pavel Kirilenko,Kazuhiro Ohkawa,Martin Velazquez-Rizo,Zhe Zhuang,Daisuke Iida

doi:10.3390/cryst11091123

Pavel Kirilenko, Kazuhiro Ohkawa + Show 3 more

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https://doi.org/10.3390/cryst11091123

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Journal: Crystals	Publication Date: Sep 15, 2021
Citations: 9	License type: CC BY 4.0

Affiliation: King Abdullah University of Science and Technology

Abstract

We fabricated indium gallium nitride (InGaN) red light-emitting diodes (LEDs) with a peak emission wavelength of 649 nm and investigated their electroluminescence (EL) properties. An additional separated peak in the EL spectrum of the red LEDs at 20 mA was observed at 465 nm. This additional peak also exhibits a blue-shift with increasing currents as does the main emission peak. Using high-resolution microscopy, we observed many point-like emission spots in the EL emission images at the currents below 1 mA. However, these emission spots cannot be identified at currents above 5 mA because the red emission from quantum wells (QWs) is much stronger than that emitted by these spots. Finally, we demonstrate that these emission spots are related to the defects generated in red QWs. The measured In content was lower at the vicinity of the defects, which was regarded as the reason for separated short-wavelength emission in red InGaN LEDs.

Highlights

III-nitride semiconductors have become popular materials for constructing lightemitting diodes (LEDs) as a result of several breakthroughs in the epitaxial growth, doping techniques, and device performances of these semiconductors [1,2,3,4]
The presence of the additional emission in high-In-content indium gallium nitride (InGaN) LEDs is generally attributed to the poor miscibility between InN and GaN [19]
Lower compared to other areas of higher brightness. This region corresponded to the separated emission and exhibited a shorter wavelength emission than the red quantum wells (QWs), a finding that was consistent with the EL spectrum and mappings

Summary

Introduction

III-nitride semiconductors have become popular materials for constructing lightemitting diodes (LEDs) as a result of several breakthroughs in the epitaxial growth, doping techniques, and device performances of these semiconductors [1,2,3,4]. The long-wavelength emitting InGaN LEDs show additional emission peaks in the blue-green range in their electroluminescence (EL) spectra [8,15,16,17,18]. In phase separation tends to appear because of the strain caused by lattice mismatch in the active region [20] All of these phenomena would lead to the in concentration fluctuation in the high-In-content InGaN QWs and possibly result in the additional emission. The. In this study, we observed the additional emission component from the EL spectru2mof 7 of our red InGaN LEDs. The emission behaviors of the additional component were first investigated using EL measurements at different currents at room temperature (RT). EL mappings under high-resolution microscopy were used to examine the luminescence paEtLtermnaspapt idnigffseruenndtecruhrrigenht-sr.eBsoyluptrieocnismelyicrmoascrokpinygwtheerepuossietdiotnoseoxfatmheinloectahleizleudmeimneissscieonnce sppoattst,ewrnesfaint adlilfyfemreenatsucurerrdetnhtes.sBtryupctruerceissealyndmealrekminegnttshoefpthoseitloiocnaslizoef dtheemloiscsailoiznesdpeomts iasnsidon prsopvoitdse, dwde ifirencatlleyvmideeanscuerefodrtthheesotrruigcitnuroefstahnedadeldeimtioenntasl osfhtohret-lwocaavleizleendgetmh eismsiiosnsisopno. ts and provided direct evidence for the origin of the additional short-wavelength emission

Materials and Methods

Findings

Conclusions