Poole-Frenkel Effect and Phonon-Assisted Tunneling in GaAs Nanowires

TL;DR

This study investigates the electronic transport mechanisms in GaAs nanowires, revealing trap-mediated conduction, Poole-Frenkel effects, and phonon-assisted tunneling, with implications for understanding their resistive behavior despite high impurity doping.

Contribution

It provides experimental evidence of trap-mediated transport and field-dependent tunneling in GaAs nanowires, highlighting the fundamental physics governing their electrical properties.

Findings

GaAs nanowires are highly resistive despite doping

Poole-Frenkel transport observed at low fields

Phonon-assisted tunneling dominates at high fields

Abstract

We present electronic transport measurements of GaAs nanowires grown by catalyst-free metal-organic chemical vapor deposition. Despite the nanowires being doped with a relatively high concentration of substitutional impurities, we find them inordinately resistive. By measuring sufficiently high aspect-ratio nanowires individually in situ, we decouple the role of the contacts and show that this semi-insulating electrical behavior is the result of trap-mediated carrier transport. We observe Poole-Frenkel transport that crosses over to phonon-assisted tunneling at higher fields, with a tunneling time found to depend predominantly on fundamental physical constants as predicted by theory. By using in situ electron beam irradiation of individual nanowires we probe the nanowire electronic transport when free carriers are made available, thus revealing the nature of the contacts.