Limit of the electrostatic doping in two-dimensional electron gases of LaXO3 (X = Al, Ti)/SrTiO 3

• Published in: Scientific reports Vol. 4
• Main Authors: Biscaras, J, Hurand, S., Feuillet-Palma, C, Rastogi, A., Budhani, R. C., Reyren, N, Lesne, E, Lesueur, J., Bergeal, N
• Format: Journal Article
• Language: English
• Published: Nature Publishing Group 27-10-2014
• Subjects: Electronics; Engineering Sciences
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/srep06788

In LaTiO3/SrTiO3 and LaAlO3/SrTiO3 heterostructures, the bending of the SrTiO3 conduction band at the interface forms a quantum well that contains a superconducting two-dimensional electron gas (2-DEG). Its carrier density and electronic properties, such as superconductivity and Rashba spin-orbit coupling can be controlled by electrostatic gating. In this article we show that the Fermi energy lies intrinsically near the top of the quantum well. Beyond a filling threshold, electrons added by electrostatic gating escape from the well, hence limiting the possibility to reach a highly-doped regime. This leads to an irreversible doping regime where all the electronic properties of the 2-DEG, such as its resistivity and its superconducting transition temperature, saturate. The escape mechanism can be described by the simple analytical model we propose.