Dopant solubility and charge compensation in La-doped SrSnO3 films

Abstract

We investigate lanthanum (La) as an n-type dopant in the strain-stabilized tetragonal phase of SrSnO3 grown on GdScO3 (110) using a radical-based hybrid molecular beam epitaxy approach. Fully coherent, epitaxial films with an atomically smooth film surface were obtained irrespective of doping density. By combining secondary ion mass spectroscopy and Hall measurements, we demonstrate that each La atom contributes one free electron to the film, confirming that it occupies the Sr site in SrSnO3 and that it is completely activated. Carrier density exceeding 1 × 1020 cm-3 was achieved in La-doped SrSnO3 films, which is in excellent agreement with the dopant-solubility limit predicted by density functional theory calculations. A record-high room-temperature mobility of 70 cm2 V-1 s-1 at 1 × 1020 cm-3 was obtained in a 12 nm La-doped SrSnO3 film, making this the thinnest perovskite oxide semiconductor with electron mobility exceeding 25 cm2 V-1 s-1 at room temperature. We discuss the structure-dopant-transport property relationships, providing essential knowledge for the design of electronic devices using these materials.