Abstract
We present a study of electron gas properties in InAs nanowires determined by interaction between nanowire geometry, doping and surface states. The electron gas density and space distribution are calculated via self-consistent solution of coupled Schroedinger and Poisson equations in the nanowires with a hexagonal cross-section. We show that the density of surface states and the nanowire width define the spatial distribution of the electrons. Three configurations can be distinguished, namely the electrons are localized in the center of the wire, or they are arranged in a uniform tubular distribution, or finally in a tubular distribution with additional electron accumulation at the corners of the nanowire. The latter one is dominating for most experimentally obtained nanowires. N-type doping partly suppresses electron accumulation at the nanowire corners. The electron density calculated for both, various nanowire widths and different positions of the Fermi level at the nanowire surface, is compared with the experimental data for intrinsic InAs nanowires. Suitable agreement is obtained by assuming a Fermi level pinning at 60 to 100 meV above the conduction band edge, leading to a tubular electron distribution with accumulation along the corners of the nanowire.
Highlights
Electron and hole gas in semiconductor nanowires of the sizes compared to the de Broglie wavelength is a fascinating object since its properties are determined by quantum-mechanical effects
We evaluate the ratio of electrons accumulated in the corners to those confined along the nanowire facets in dependence on the nanowire geometry as well as on nanowire doping
In n-doped nanowires the Fermi level lies not further than 0.1 eV below or above the neutrality level. Being armed with this knowledge, in the present theoretical study we describe the surface more generally, namely without introducing a specific type of the surface states energy distribution, we assign a certain position to the conduction band edge with respect to the Fermi level at the nanowire surface
Summary
In our theoretical study we consider InAs nanowires similar to those reported in ref. The increase in the surface states density leads to a shift of the Fermi level towards the neutrality level where it is pinned in both intrinsic and n-doped nanowires as soon as the surface states density exceeds 1012 cm−2. In n-doped nanowires the Fermi level lies not further than 0.1 eV below or above the neutrality level Being armed with this knowledge, in the present theoretical study we describe the surface more generally, namely without introducing a specific type of the surface states energy distribution, we assign a certain position to the conduction band edge with respect to the Fermi level at the nanowire surface. As we showed above it can be related to the total density of surface states and for each model of the surface this relation might be rather different
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