Structural and Optical Emission Uniformity of m-Plane InGaN Single Quantum Wells in Core–Shell Nanorods

Emmanuel D Le Boulbar,Chris R Bowen,Colin J Humphreys,Shahrzad Hosseini Vajargah,Ionut Gîrgel,Philip A Shields,Paul R Edwards,Ian Griffiths,Duncan W E Allsopp,Robert W Martin,Pierre-Marie Coulon,David Cherns

doi:10.1021/acs.cgd.5b01438

Emmanuel D Le Boulbar, Chris R Bowen + Show 10 more

Open Access

https://doi.org/10.1021/acs.cgd.5b01438

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Abstract

Controlling the long-range homogeneity of core–shell InGaN/GaN layers is essential for their use in light-emitting devices. This paper demonstrates variations in optical emission energy as low as ∼7 meV·μm–1 along the m-plane facets from core–shell InGaN/GaN single quantum wells as measured through high-resolution cathodoluminescence hyperspectral imaging. The layers were grown by metal organic vapor phase epitaxy on etched GaN nanorod arrays with a pitch of 2 μm. High-resolution transmission electron microscopy and spatially resolved energy-dispersive X-ray spectroscopy measurements demonstrate a long-range InN-content and thickness homogeneity along the entire 1.2 μm length of the m-plane. Such homogeneous emission was found on the m-plane despite the observation of short-range compositional fluctuations in the InGaN single quantum well. The ability to achieve this uniform optical emission from InGaN/GaN core–shell layers is critical to enable them to compete with and replace conventional planar light-e...

Highlights

I nGaN/GaN core−shell nanorod light emitting diodes (LEDs) have the potential to overcome the limitations of current-generation planar devices
The growth of such InGaN quantum wells (QWs) on NRs often suffers from a gradient in InGaN composition and thickness along the nonpolar length of the nanorods.[3−6] While this phenomenon can be exploited for applications requiring broad absorption or emission bands, it will lead to strong emission wavelength shifts with drive current
In comparison to QWs in a conventional c-plane MQWs LED, all can be classified as a wide single quantum well (SQW), being wider than the expected exciton Bohr radius.[27]

Summary

Introduction

I nGaN/GaN core−shell nanorod light emitting diodes (LEDs) have the potential to overcome the limitations of current-generation planar devices. The uniformity of the optical emission of the GaN/InGaN/ GaN core−shell structures was assessed by room-temperature high-resolution cathodoluminescence (CL) hyperspectral imaging.[32] The measurement conditions can be found in the Experimental Details.

Results

Conclusion