Density control of GaN nanowires at the wafer scale using self-assembled SiN${}_x$ patches on sputtered TiN(111)

Abstract

The self-assembly of heteroepitaxial GaN nanowires using either molecular beam epitaxy (MBE) or metal-organic vapor phase epitaxy (MOVPE) mostly results in wafer-scale ensembles with ultrahigh ($>10$ $\mu$m${}^{-2}$) or ultralow ($<1$ $\mu$m${}^{-2}$) densities, respectively. A simple means to tune the density of well-developed nanowire ensembles between these two extremes is generally lacking. Here, we examine the self-assembly of SiN${}_x$ patches on TiN(111) substrates which are eventually acting as seeds for the growth of GaN nanowires. We first found that if prepared by reactive sputtering, the TiN surface is characterized by \{100\} facets for which the GaN incubation time is extremely long. Fast GaN nucleation is only obtained after deposition of a sub-monolayer of SiN${}_x$ atoms prior to the GaN growth. By varying the amount of pre-deposited SiN${}_x$, the GaN nanowire density could be tuned by three orders of magnitude with excellent uniformity over the entire wafer, bridging the density regimes conventionally attainable by direct self-assembly with MBE or MOVPE. The analysis of the nanowire morphology agrees with a nucleation of the GaN nanowires on nanometric SiN${}_x$ patches. The photoluminescence analysis of single freestanding GaN nanowires reveals a band edge luminescence dominated by excitonic transitions that are broad and blue shifted compared to bulk GaN, an effect that is related to the small nanowire diameter and to the presence of a thick native oxide. The approach developed here can be principally used for tuning the density of most III-V semiconductors nucleus grown on inert surfaces like 2D materials.

References in corpus (11)

• Bright single-photon sources in bottom-up tailored nanowires
• A growth diagram for plasma-assisted molecular beam epitaxy of GaN nanocolumns on Si(111)
• Self-regulated radius of spontaneously formed GaN nanowires in molecular beam epitaxy
• Molecular Beam Epitaxy of GaN Nanowires on Epitaxial Graphene
• Observation of dielectrically confined excitons in ultrathin GaN nanowires up to room temperature
• Monitoring the formation of nanowires by line-of-sight quadrupole mass spectrometry: a comprehensive description of the temporal evolution of GaN nanowire ensembles
• Correlation between the structural and optical properties of spontaneously formed GaN nanowires: a quantitative evaluation of the impact of nanowire coalescence
• Self-Assembled formation of long, thin, and uncoalesced GaN nanowires on crystalline TiN films
• Polarity-induced selective area epitaxy of GaN nanowires
• A route for the top-down fabrication of ordered ultrathin GaN nanowires
• X-ray scattering study of GaN nanowires grown on Ti/Al${}_2$O${}_3$ by molecular beam epitaxy

Cited by in corpus (2)

• ScN/GaN($1\bar{1}00$): a new platform for the epitaxy of twin-free metal-semiconductor heterostructures
• Growth kinetics and substrate stability during high-temperature molecular beam epitaxy of AlN nanowires