Suppressed carrier density for the patterned high mobility two-dimensional electron gas at γ-Al₂O₃/SrTiO₃ heterointerfaces

The two-dimensional electron gas (2DEG) at the non-isostructural interface between spinel γ-Al2O3 and perovskite SrTiO3 is featured by a record electron mobility among complex oxide interfaces in addition to a high carrier density up to the order of 10¹⁵ cm^-2. Herein, we report on the patterning of 2DEG at the γ-Al2O3/SrTiO3 interface grown at 650 °C by pulsed laser deposition using a hard mask of LaMnO3. The patterned 2DEG exhibits a critical thickness of 2 unit cells γ-Al2O3 for the occurrence of interface conductivity, similar to the unpatterned sample. However, its maximum carrier density is found to be approximately 3×1013 cm-2, much lower than that of the unpatterned sample (~10¹⁵ cm^-2). Remarkably, a high electron mobility of approximately 3,600 cm²V^-1s^-1 was obtained at low temperatures for the patterned 2DEG at a carrier density of ~ 7×10¹² cm^-2, which exhibits clear Shubnikov-de Hass quantum oscillations. The patterned high-mobility 2DEG at the γ-Al2O3/SrTiO3 interface paves the way for the design and application of spinel/perovskite interfaces for high-mobility all-oxide electronic devic