Transport characterization in nanowires using an electrical nanoprobe

Abstract

Electrical transport in semiconductor nanowires is commonly measured in a field effect transistor configuration, with lithographically defined source, drain, and in some cases, top gate electrodes. This approach is labor intensive, requires high-end fabrication equipment, exposes the nanowires to extensive processing chemistry, and places practical limitations on minimum nanowire length. Here we describe a simple method for characterizing electrical transport in nanowires directly on the growth substrate, without any need for post growth processing. Our technique is based on contacting nanowires using a nano-manipulator probe retrofitted inside of a scanning electron microscope. Using this approach we characterize electrical transport in GaN nanowires grown by catalyst-free selective epitaxy, as well as InAs and Ge nanowires grown by Au-catalyzed vapor solid liquid technique. We find that in situations where contacts are not limiting carrier injection (GaN and InAs nanowires), electrical transport transitions from Ohmic conduction at low bias, to space-charge limited conduction at higher bias. Using this transition and a theory of space charge limited transport which accounts for the high aspect ratio nanowires, we extract the mobility and the free carrier concentration. For Ge nanowires, we find that the Au catalyst forms a Schottky contact resulting in rectifying current-voltage characteristics, and which are strongly dependent on the nanowire diameter. This dependence arises due to increase in depletion width at decreased nanowire diameter and carrier recombination at the nanowire surface.

β-Ga2O3 nanowires for an ultraviolet light selective frequency photodetector

“…This result indicates the existence of an additional charging/discharging current flowing on increase/decrease of the voltage. The non-linear behaviour is consistent with previous reports on different materials, such as ZnO, GaN or InAs, in which it was associated to space-charged-limited current (SCLC) [24][25][26]. The SCLC suggests the existence of two conduction regimens.…”

Strong Schottky barrier reduction at Au-catalyst/GaAs-nanowire interfaces by electric dipole formation and Fermi-level unpinning

“…Series B NWs with different doping profiles (fully n-type, half-way-doped n-type and nominally undoped) were characterized with I-V measurements using STM 33 . Several NWs of the same type were characterized in this way.…”

Observation of Space-Charge-Limited Transport in InAs Nanowires

“…By controllably inducing failure by Joule heating, we show that electrical transport is dominated by the bulk of the NW instead of the contacts, a further indication of SCL transport. The two-point probe method we employ [7] is performed in-vacuo on freestanding wires thus diminishing the electrical and thermal influence of molecular adsorbates and the substrate on which NW devices typically lie.…”