Issue 17, 2021

Selective area grown AlInGaN nanowire arrays with core–shell structures for photovoltaics on silicon

Abstract

To pave the way for InGaN-on-Si integrated photovoltaics, uniform and close-packed n-GaN/(Al)InGaN/p-GaN nanowire (NW) arrays with a ∼0.29 μm thick absorption segment of ∼2.35 eV energy bandgap were fabricated on a Si substrate using Ti-mask selective area growth (SAG) in a molecular beam epitaxy (MBE) chamber. Instead of using thick and insulting buffer layers, this SAG process was realized by employing a 3 nm AlN/GaN: Ge buffer layer to facilitate electrical and thermal conduction between NWs and Si. Scanning transmission electron microscopy and high-resolution electron energy loss spectroscopy mapping revealed the discontinuities of AlN and the embedments of GaN:Ge which contribute to a negligible resistance of the NWs-on-Si interface. AlInGaN active segment exhibits core–shell structures, which suppress nonradiative surface recombination at NW surfaces. Working of AlInGaN core–shell NW solar cells was demonstrated with improved open-circuit voltage (Voc) and higher energy conversion efficiency (η) than those reported for InGaN NW solar cells. Stable output characteristics including the Voc of 1.41 V and η of 2.46% were obtained under 30-Sun illuminations. Such NWs-on-Si devices use Si substrate as the bottom electrode. With a low series resistance of ∼1 Ω, this work paves the way to monolithically integrate MBE-SAG III-nitride devices and Si-based electronics, such as Si solar cells and CMOS devices.

Graphical abstract: Selective area grown AlInGaN nanowire arrays with core–shell structures for photovoltaics on silicon

Supplementary files

Article information

Article type
Paper
Submitted
22 Jan 2021
Accepted
01 Apr 2021
First published
08 Apr 2021

Nanoscale, 2021,13, 8163-8173

Selective area grown AlInGaN nanowire arrays with core–shell structures for photovoltaics on silicon

R. Wang, S. Cheng, S. Vanka, G. A. Botton and Z. Mi, Nanoscale, 2021, 13, 8163 DOI: 10.1039/D1NR00468A

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