Enhanced carrier densities in two-dimensional electron gas formed at BaSnO3/SrTaO3 and SrSnO3/SrTaO3 interfaces

Abstract

Two-dimensional electron gases (2DEGs) realized at perovskite oxide interfaces offer great promise for high charge carrier concentrations and low-loss charge transport. BaSnO3 (BSO) and SrSnO3 (SSO) are well-known wide bandgap semiconductors for their high mobility due to the Sn-5s-dominated conduction band minimum (CBM). Ta4+ with a 5d1 valence configuration in SrTaO3 (STaO) injects the d1 electron across the interface into the unoccupied Sn-5s states in BSO and SSO. The present study uses ACBN0 density functional theory computations to explore charge transfer and 2DEG formation at BSO/STaO and SSO/STaO interfaces. The results of the ACBN0 computations confirm the Ta-5d to Sn-5s charge transfer. Moreover, the Sn-5s-dominated CBM is located ∼1.4 eV below the Fermi level, corresponding to an excess electron density in BSO of ∼1.5 × 1021 cm−3, a ∼50% increase in electron density compared to the previously studied BSO/SrNbO3 (SNO) interface. Similarly, the SSO/STaO interface shows an improvement in interface electron density by ∼20% compared to the BSO/SNO interface. The improved carrier density in SSO/STaO and BSO/STaO is further supported by ∼13% and ∼15% increase in electrical conductivities compared to BSO/SNO. In summary, BSO/STaO and SSO/STaO interfaces provide novel material platforms for 2DEGs formation and ultra-low-loss electron transport.