High Mobility Two-Dimensional Electron Gas in BaSnO₃/SrNbO₃ Interface

Two-dimensional electron gases (2DEGs) realized at interfaces offer great promise for high charge carrier concentrations and low-loss charge transport. BaSnO₃ (BSO) is well-known for its high mobility due to its Sn-5s dominated conduction band minimum (CBM). Nb⁴⁺ with d¹ valence configuration in SrNbO₃ (SNO) may inject the d¹ electron across the interface into the unoccupied Sn-5s states in BSO. In the present study, we use the synergy of ACBN0 computations and experiment to explore the charge transfer and 2DEG formation at BSO/SNO interfaces. The results of the ACBN0 computations confirm the intended Nb-4d to Sn-5s charge transfer. Moreover, the Sn-5s CMB is located up to ~1.2 eV below the Fermi level, corresponding to an excess electron density in BSO of ~10²¹ cm^-3. Our angle-resolved X-ray photoelectron spectroscopy experiments for BSO/SNO interfaces grown by molecular beam epitaxy suggest an even higher electron density of ~4×10²¹ cm^-3. This charge density discrepancy is attributed to a slight overestimation of the bandgap in the computation relative to experiment. In summary, consistency of theory and the experiments shows that BSO/SNO interfaces provide a novel rational materials platform for 2DEG formation and ultra-low loss electron transport.