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

Abstract

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.

Large Linear Magnetoresistance of High‐Mobility 2D Electron System at Nonisostructural γ‐Al2O3/SrTiO3 Heterointerfaces

“…Since this large MR is rare in oxide 2DESs, we summarize the typical MR ratios for different oxide‐based conducting interfaces or surfaces (note that the MR ratio is highly sample‐, temperature‐, and magnetic field‐dependent, we therefore just summarize MR at 8 T below 5 K, which is accessible for most transport facilities), as shown in Figure . It is obvious that the MR ratio of the GAO/STO interface is higher than the other oxide interfaces, including LAO/STO, [ 42,57–63 ] CaZrO 3 /SrTiO 3 (CZO/STO), [ 64,65 ] LaTiO 3 /SrTiO 3 (LTO/STO), [ 66 ] amorphous‐LAO/KTaO 3 (a‐LAO/KTO), [ 43,67 ] Sr 3 Al 2 O 6 /STO (SAO/STO), [ 12 ] extrinsic STO conducting surface, [ 54,68,69 ] and even bulk STO. [ 27,70,71 ] Based on the substantial MR above, a general qualitative picture could be constructed: MR ratio has a close relationship with the mobility.…”

Probing surfaces and interfaces in complex oxide films via in situ X-ray photoelectron spectroscopy

“…In the case of KTaO 3 , surface 2DEGs have been reported in ultrahigh vacuum conditions from oxygen vacancies [33,34]. Since these reports, a variety of means have been developed to produce interfacial 2DEGs in KTaO 3 , primarily through the introduction of polar/non-polar interfaces [35,36,37]. These interfaces have exhibited such interesting properties as optically tunable Rashba effect and greater Hall mobility than analogous LaAlO 3 /SrTiO 3 interfaces.…”

Tuning the Electrical State of 2DEG at LaVO3−KTaO3 Interface: Effect of Light and Electrostatic Gate

“…It has been reported that conductivity tuning with light illumination is possible for KTO. [ 47,48 ] Only a few reports on the photoconductivity of oxygen vacant conducting KTO are available. [ 49 ] But the effect on the electrical conductivity of 2DEG in KTO under light and/or gate is not well explored.…”