Highly Mobile Two-Dimensional Electron Gases with Strong Gating Effect at the Amorphous-LaAlO₃/KTaO₃ Interface

Two-dimensional electron gas (2DEG) at 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 SrTiO₃-based 2DEG, we demonstrate the fabrication of high quality 2DEGs by growing an amorphous LaAlO₃ layer on a (001)-orientated KTaO₃ substrate, which is a 5d-metal oxide with a polar surface, at a high temperature that is usually adopted for crystalline LaAlO₃. Metallic 2DEGs with the Hall mobility as high as ~2150 cm²/Vs and the sheet carrier density as low as 2×10¹² cm^-2 are obtained. For the first time, gating effect on transport process is studied, and its influence on spin relaxation, inelastic and elastic scattering are determined. Remarkably, the spin relaxation time can be strongly tuned by back gate. It is reduced by a factor of ~69 while sweeping gate voltage from -25 V to 100 V. The mechanism that dominates the spin relaxation is elucidated.