Electrostatic carrier doping of GdTiO3/SrTiO3 interfaces

TL;DR

This study demonstrates electrostatic carrier doping at GdTiO3/SrTiO3 interfaces, revealing a high-density two-dimensional electron gas formed through intrinsic electronic reconstruction, with implications for interface engineering in oxide heterostructures.

Contribution

It provides experimental evidence of electrostatic doping and detailed insights into charge distribution and band alignment at GdTiO3/SrTiO3 interfaces.

Findings

Carrier densities are independent of layer thicknesses.

High concentration 2D electron gas is confined at the interface.

Electrostatic requirements are met by the observed carrier densities.

Abstract

Heterostructures and superlattices consisting of a prototype Mott insulator, GdTiO3, and the band insulator SrTiO3 are grown by molecular beam epitaxy and show intrinsic electronic reconstruction, approximately 1/2 electron per surface unit cell at each GdTiO3/SrTiO3 interface. The sheet carrier densities in all structures containing more than one unit cell of SrTiO3 are independent of layer thicknesses and growth sequences, indicating that the mobile carriers are in a high concentration, two-dimensional electron gas bound to the interface. These carrier densities closely meet the electrostatic requirements for compensating the fixed charge at these polar interfaces. Based on the experimental results, insights into interfacial band alignments, charge distribution and the influence of different electrostatic boundary conditions are obtained.