Engineering decomposition-resilience and de-coalescence of GaN nanowire ensembles

TL;DR

This paper presents a novel method using an AlN cap layer to suppress thermal decomposition and coalescence in GaN nanowire ensembles, improving their suitability for optoelectronic applications.

Contribution

The study introduces a simple AlN capping technique that effectively prevents GaN nanowire decomposition and coalescence during growth and post-processing.

Findings

AlN capping nearly completely suppresses GaN NW thermal decomposition.

Post-annealing, uncapped NWs decompose selectively, leaving superior capped NWs.

Enhanced crystal quality and luminescence in capped GaN NWs.

Abstract

The rapidly increasing interest in nanowires (NWs) of GaN and associated III-Nitrides for (opto-)electronic applications demands immediate addressal of the technological challenges associated with both NW-growth and device processing. Towards this end, we demonstrate in this work an approach to suppress thermal decomposition of GaN NWs, which also serves to remedy the effect of NW-coalescence during growth. While both these effects are well-known to be major hurdles in the development of GaN-NW-devices, reliable methods to tackle these issues have not been reported so far. We show that by providing a thin AlN cap layer, which epitaxially grows only on the top-facet of the GaN NWs, thermal decomposition can be almost completely suppressed. Thermal annealing of GaN NW-ensembles, post AlN-capping, leads to selective decomposition of uncapped/partially-capped NWs, leaving behind (mostly) AlN-capped GaN NWs, with superior crystal- and luminescence characteristics. This simple yet extremely effective approach may therefore serve as a very crucial milestone in the roadmap of GaN-NW-based (opto-)electronic technology.