Separating Electrons and Donors in BaSnO₃ via Band Engineering

Separating electrons from their source atoms in La-doped BaSnO₃, the first perovskite oxide semiconductor to be discovered with high room-temperature electron mobility, remains a subject of great interest for achieving high-mobility electron gas in two dimensions. So far, the vast majority of work in perovskite oxides has focused on heterostructures involving SrTiO₃ as an active layer. Here we report the demonstration of modulation doping in BaSnO₃ as the high room-temperature mobility host without the use of SrTiO₃. Significantly, we show the use of angle-resolved hard X-ray photoelectron spectroscopy (HAXPES) as a nondestructive approach to not only determine the location of electrons at the buried interface but also to quantify the width of electron distribution in BaSnO₃. The transport results are in good agreement with the results of self-consistent solution to one-dimensional Poisson and Schrödinger equations. Finally, we discuss viable routes to engineer two-dimensional electron gas density through band-offset engineering.