Electron transport at interface of LaAlO₃ and SrTiO₃ band insulators

Electron transport properties at n-type LaAlO₃/SrTiO₃ interfaces have been investigated numerically. Carrier distributions, band structures, and sheet density have been calculated by solving Schrödinger equations with Poisson equation in a self-consistent manner for various LaAlO₃/SrTiO₃ interfaces with and without atomic interdiffusions. It was found that the interface with A-site atom interdiffusion has the critical thickness of 4 unit cells below which it remains insulating. Most electrons are localized within 10 nm from the interface forming two-dimensional electron gas and multi-subbands are occupied indicating the multi-channel conduction. Electron mobility along the A-site atom interdiffused interface has been calculated using the linearized Boltzmann transport equation including scattering mechanisms of acoustic phonon, polar optical phonon, interface roughness, and net charged layers. At low temperature, the mobility is limited by the interface roughness and net charged layers. At room temperature, the polar optical phonon is the dominant electron scattering mechanism and the mobility is almost independent from the thickness of LaAlO₃ film.