Spontaneous nucleation and growth of GaN nanowires: Fundamental role of crystal polarity

Abstract

We experimentally investigate whether crystal polarity affects the growth of GaN nanowires in plasma-assisted molecular beam epitaxy and whether their formation has to be induced by defects. For this purpose, we prepare smooth and coherently strained AlN layers on 6H-SiC(0001) and SiC(000$\bar{1}$) substrates to ensure a well-defined polarity and an absence of structural and morphological defects. On N-polar AlN, a homogeneous and dense N-polar GaN nanowire array forms, evidencing that GaN nanowires form spontaneously in the absence of defects. On Al-polar AlN, we do not observe the formation of Ga-polar GaN NWs. Instead, sparse N-polar GaN nanowires grow embedded in a Ga-polar GaN layer. These N-polar GaN nanowires are shown to be accidental in that the necessary polarity inversion is induced by the formation of Si${}_x$N. The present findings thus demonstrate that spontaneously formed GaN nanowires are irrevocably N-polar. Due to the strong impact of the polarity on the properties of GaN-based devices, these results are not only essential to understand the spontaneous formation of GaN nanowires but also of high technological relevance.

References in corpus (4)

• A growth diagram for plasma-assisted molecular beam epitaxy of GaN nanocolumns on Si(111)
• In situ GaN decomposition analysis by quadrupole mass spectrometry and reflection high-energy electron diffraction
• In situ investigation of growth modes during plasma-assisted molecular beam epitaxy of (0001)GaN
• Compared growth mechanisms of Zn-polar ZnO nanowires on O-polar ZnO and on sapphire

Cited by in corpus (7)

• Self-regulated radius of spontaneously formed GaN nanowires in molecular beam epitaxy
• Molecular Beam Epitaxy of GaN Nanowires on Epitaxial Graphene
• 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
• Investigating the origin of the nonradiative decay of bound excitons in GaN nanowires
• Polarity-induced selective area epitaxy of GaN nanowires
• Nature of excitons bound to inversion domain boundaries: Origin of the 3.45-eV luminescence lines in spontaneously formed GaN nanowires on Si(111)