Highly Mobile Two-Dimensional Electron Gases with a Strong Gating Effect at the Amorphous LaAlO/KTaO Interface.

Two-dimensional electron gas (2DEG) at the perovskite oxide interface exhibits a lot of exotic properties, presenting a promising platform for the exploration of emergent phenomena. While most of the previous works focused on SrTiO-based 2DEG, here we report on the fabrication of high-quality 2DEGs by growing an amorphous LaAlO layer on a (001)-orientated KTaO substrate, which is a 5d metal oxide with a polar surface, at a high temperature that is usually adopted for crystalline LaAlO. Metallic 2DEGs with a Hall mobility as high as ∼2150 cm/(V s) and a sheet carrier density as low as 2 × 10 cm are obtained. For the first time, the gating effect on the transport process is studied, and its influence on spin relaxation and inelastic and elastic scattering is determined. Remarkably, the spin relaxation time can be strongly tuned by a back gate. It is reduced by a factor of ∼69 while the gate voltage is swept from -25 to +100 V. The mechanism that dominates the spin relaxation is elucidated.