Modulation doping in LaInO₃/BaSnO₃ polar interface

A transparent perovskite oxide, BaSnO₃ (BSO), has started to attract a great deal of attention due to its high room temperature mobility (μ) and oxygen stability. Among various heterostructures based on BaSnO₃, the two dimensional electron gas-like state at the LaInO₃(LIO)/Ba_1-xLa_xSnO₃(BLSO) polar interface is most interesting because the interface exhibits a sheet conductance enhancement up to several orders of magnitude between two band insulators. Here we investigate the transport property of the modulated polar interface in LIO/BSO/BLSO heterostructures. Both the carrier density (n_s) and the Hall mobility (μ_H) continually decrease while increasing the thickness of the BSO spacer layer (d) at the interface, indicating a changing electron density profile as a function of the thickness, which can be confirmed by self-consistent 1D Poisson-Schrodinger calculation. The sharp decrease of n_s makes it difficult to see the effect of spacer layer in modulated structures due to simultaneous decrease of μ caused by Coulomb scattering from ionized donors. Hence we controlled the band bending continuously via field effect with a fixed spacer thickness, leading to the observation of the enhanced mobility (μ_FE) in the modulated heterostructures.