Photocurrents in a Single InAs Nanowire/ Silicon Heterojunction

TL;DR

This study explores the optoelectronic behavior of single InAs nanowire/silicon heterojunctions, revealing trap-assisted charge transport, photovoltaic effects, and photoconductance phenomena through scanning photocurrent microscopy.

Contribution

It provides new insights into charge transport mechanisms and optoelectronic properties of InAs nanowire/silicon heterojunctions using advanced microscopy techniques.

Findings

Trap states facilitate charge transport across heterojunctions.

Photovoltaic effect observed at small bias voltages.

Photoconductance effect within nanowires at large biases.

Abstract

We investigate the optoelectronic properties of single indium arsenide nanowires, which are grown vertically on p-doped silicon substrates. We apply a scanning photocurrent microscopy to study the optoelectronic properties of the single heterojunctions. The measured photocurrent characteristics are consistent with an excess charge carrier transport through mid-gap trap states, which form at the Si/InAs heterojunctions. Namely, the trap states add an additional transport path across a heterojunction, and the charge of the defects changes the band bending at the junction. The bending gives rise to a photovoltaic effect at a small bias voltage. In addition, we observe a photoconductance effect within the InAs nanowires at large biases.