The effect of fabrication conditions on 2DEGs transport characteristics at amorphous-LaAlO3/KTaO3 interfaces

Abstract

Two-dimensional electron gases (2DEGs) formed at the interface between two oxide insulators present a promising platform for the exploration of emergent phenomena. While most of the previous works focused on SrTiO3-based 2DEGs, here we report on a systematic investigation of the 2DEGs at amorphous-LaAlO3/KTaO3 (a-LAO/KTO) interfaces, focusing on the effect of fabrication conditions on 2DEGs. We found that 2DEGs can be formed in a wide temperature range from room temperature to 750° under the oxygen pressure 1 × 10–4 Pa. Unexpectedly, its performance shows a unusual strong dependence on fabrication temperature: the Hall mobility increases rapidly with the decrease of substrate temperature. The highest extracted mobility of charge carriers coming from dXZ/dYZ subband is ∼6.6 × 103 cm2 V−1s−1, achieved under the condition of TS = 100 °C and PO2 = 3 × 10–5 Pa. This value is higher than that of the 2DEGs of a-LAO/SrTiO3 by a factor of 30, which reveals the unique character of the 2DEGs formed by 5d electrons. Two-band model is applied for the analysis of the transport behavior, from which information on carrier density and Hall mobility and their dependence on fabrication conditions are determined.