III-nitride core\u2013shell nanorod array on quartz substrates

Si-Young Bae,Yong-Tak Lee,Jung-Wook Min,Kaddour Lekhal,Young-Dahl Jho,Dong-Seon Lee,Hyeong-Yong Hwang,Hiroshi Amano,Nobuyuki Ikarashi,Ho-Jun Lee,Yoshio Honda

doi:10.1038/srep45345

Si-Young Bae, Yong-Tak Lee + Show 9 more

Open Access

https://doi.org/10.1038/srep45345

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Abstract

We report the fabrication of near-vertically elongated GaN nanorods on quartz substrates. To control the preferred orientation and length of individual GaN nanorods, we combined molecular beam epitaxy (MBE) with pulsed-mode metal–organic chemical vapor deposition (MOCVD). The MBE-grown buffer layer was composed of GaN nanograins exhibiting an ordered surface and preferred orientation along the surface normal direction. Position-controlled growth of the GaN nanorods was achieved by selective-area growth using MOCVD. Simultaneously, the GaN nanorods were elongated by the pulsed-mode growth. The microstructural and optical properties of both GaN nanorods and InGaN/GaN core–shell nanorods were then investigated. The nanorods were highly crystalline and the core–shell structures exhibited optical emission properties, indicating the feasibility of fabricating III-nitride nano-optoelectronic devices on amorphous substrates.

Highlights

Large-area amorphous substrates with high-temperature (>1000 °C) endurance, such as quartz and alumina, are available at low cost
Because the selective-area growth (SAG) was performed on a patterned hole array, we defined the relative NR density as the number of grown NRs divided by the number of maximum opening holes over the same area
The relative NR density was reduced by coalescence, which decreased the number of grown NRs

Summary

Introduction

Large-area amorphous substrates with high-temperature (>1000 °C) endurance, such as quartz and alumina, are available at low cost. To solve the above problems, we here combine MBE and MOCVD with nanoscale local epitaxy (i.e. nanoscale SAG) to improve the crystal quality of GaN on amorphous layers. We reported that GaN layers can evolve on amorphous substrates through microscale SAG with striped openings, where a relatively smooth GaN buffer layer was grown by MBE without a POL27. The coalescence of adjacent GaN structures is suppressed by anisotropic growth of pulsed-mode MOCVD28, thereby leading an elongation of GaN nanorods (NRs) This growth is effective even on low-quality and thin templates[29], suggesting its applicability to epitaxy on amorphous substrates. Owing to the relevant uniformity of GaN NR array, InGaN/GaN core–shell layers are grown and their structural and optical characteristics are analysed to facilitate potential device applications

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