Localization of Two-dimensional Electron Gas in LaAlO3/SrTiO3 Heterostructures

TL;DR

This study investigates how disorder, carrier concentration, and band occupation affect the localization and conduction properties of a two-dimensional electron gas in LaAlO3/SrTiO3 heterostructures, revealing a transition from localized to metallic behavior.

Contribution

It provides new insights into the interplay between disorder, carrier density, and band occupation in controlling electron localization in oxide heterostructures.

Findings

Localization depends on interface disorder and carrier concentration.

Lower oxygen pressure increases carrier density and transitions conduction from localized to metallic.

Different Ti 3d bands have varying susceptibility to localization.

Abstract

We report strong localization of 2D electron gas in LaAlO3 / SrTiO3 epitaxial thin-film heterostructures grown on (LaAlO3)0.3-(Sr2AlTaO3)0.7 substrates by using pulsed laser deposition with in-situ reflection high-energy electron diffraction. Using longitudinal and transverse magnetotransport measurements, we have determined that disorder at the interface influences the conduction behavior, and that increasing the carrier concentration by growing at lower oxygen partial pressure changes the conduction from strongly localized at low carrier concentration to metallic at higher carrier concentration, with indications of weak localization. We interpret this behavior in terms of a changing occupation of Ti 3d bands near the interface, each with a different spatial extent and susceptibility to localization by disorder, and differences in carrier confinement due to misfit strain and point defects.