Tuning the Surface Charge Properties of Epitaxial InN Nanowires

• Published in: Nano letters Vol. 12; no. 6; pp. 2877 - 2882
• Main Authors: Zhao, S, Fathololoumi, S, Bevan, K. H, Liu, D. P, Kibria, M. G, Li, Q, Wang, G. T, Guo, Hong, Mi, Z
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 13.06.2012
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Crystallization - methods; Doping; Electron gas; Electron states and collective excitations in thin films, multilayers, quantum wells, mesoscopic and nanoscale systems; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Epitaxial growth; Exact sciences and technology; Indium - chemistry; Macromolecular Substances - chemistry; Materials science; Materials Testing; Molecular Conformation; Nanocrystalline materials; Nanoscale materials and structures: fabrication and characterization; Nanostructures - chemistry; Nanostructures - ultrastructure; Nanowires; Optical properties; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures; Particle Size; Physics; Quantum wires; Static Electricity; Surface charge; Surface Properties; Tuning; Two dimensional; Valence band; Nanowire; InN; electron accumulation; two-dimensional electron gas; photoluminescence; X-ray photoelectron spectroscopy; Valence bands; Surface charge; Electronic properties; Epitaxial layers; Epitaxy; Doping; Pinning; Theoretical study; Two-dimensional electron gas; III-V compound; Electronic structure; Fermi level; Optical properties; Growth mechanism; Surface properties; Nitrogen additions; Modelling; Indium nitride; Ab initio calculations; Nanowires; Effective mass; Nanostructured materials; Nanomaterial synthesis
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/nl300476d

We have investigated the correlated surface electronic and optical properties of [0001]-oriented epitaxial InN nanowires grown directly on silicon. By dramatically improving the epitaxial growth process, we have achieved, for the first time, intrinsic InN both within the bulk and at nonpolar InN surfaces. The near-surface Fermi-level was measured to be ∼0.55 eV above the valence band maximum for undoped InN nanowires, suggesting the absence of surface electron accumulation and Fermi-level pinning. This result is in direct contrast to the problematic degenerate two-dimensional electron gas universally observed on grown surfaces of n-type degenerate InN. We have further demonstrated that the surface charge properties of InN nanowires, including the formation of two-dimensional electron gas and the optical emission characteristics can be precisely tuned through controlled n-type doping. At relatively high doping levels in this study, the near-surface Fermi-level was found to be pinned at ∼0.95–1.3 eV above the valence band maximum. Through these trends, well captured by the effective mass and ab initio materials modeling, we have unambiguously identified the definitive role of surface doping in tuning the surface charge properties of InN.