Enhanced carrier densities in two-dimensional electron gas formed at BaSnO₃/SrTaO₃and SrSnO₃/SrTaO₃interfaces

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 5d¹valence configuration in SrTaO₃(STaO) injects thed¹electron across the interface into the unoccupied Sn-5sstates 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-5dto Sn-5scharge 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 × 10²¹cm^-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.