Molecular beam epitaxial growth and characterization of intrinsic and p-type InN nanowires

Abstract

We have investigated the molecular beam epitaxial growth and characterization of InN nanowires. Detailed optical and electrical transport studies confirm that nondoped InN nanowires can exhibit extremely low (< 10¹⁵ cm^-3) residual electron density. Furthermore, the near-surface Femi-level was measured to be 0.4 to 0.5 eV above the valence band maximum (VBM), suggesting the absence of Fermi-level pinning and surface electron accumulation. These features are fundamentally different from those of n-type degenerate InN nanowires or InN epilayers. The absence of surface electron accumulation was also observed in Mg-doped InN nanowires, where p-type conduction was directly measured via Mg-doped InN nanowire field-effect transistors. Furthermore, the near-surface Fermi-level can be tuned from 0.1 eV to 1 eV above the VBM, i.e., from p-type degenerate to n-type degenerate through controlled Mg and Si dopant incorporations, a first demonstration for any semiconducting nanowire structures.