Optically excited multi-band conduction in LaAlO3/SrTiO3 heterostructures

TL;DR

This study demonstrates that illuminating LaAlO3/SrTiO3 heterostructures with above-band-gap light significantly enhances their conductivity by creating a high-mobility electron channel, revealing multi-band conduction mechanisms.

Contribution

It provides the first detailed explanation of optically induced multi-band conduction in LaAlO3/SrTiO3 interfaces through a two-carrier model.

Findings

Resistance decreases by over 50% after illumination

Non-linear Hall resistance indicates multiple carrier types

Illumination creates a high-mobility electron channel

Abstract

The low-temperature resistance of a conducting LaAlO3/SrTiO3 interface with a 10 nm thick LaAlO3 film decreases by more than 50% after illumination with light of energy higher than the SrTiO3 band-gap. We explain our observations by optical excitation of an additional high mobility electron channel, which is spatially separated from the photo-excited holes. After illumination, we measure a strongly non-linear Hall resistance which is governed by the concentration and mobility of the photo-excited carriers. This can be explained within a two-carrier model where illumination creates a high-mobility electron channel in addition to a low-mobility electron channel which exists before illumination.