Creation and Control of Two-Dimensional Electron Gas Using Al-Based Amorphous Oxides/SrTiO3 Heterostructures Grown by Atomic Layer Deposition

The formation of a two-dimensional electron gas (2-DEG) using SrTiO3 (STO)-based heterostructures provides promising opportunities in oxide electronics. We realized the formation of 2-DEG using several amorphous layers grown by the atomic layer deposition (ALD) technique at 300 degrees C which is a process compatible with mass production and thereby can provide the realization of potential applications. We found that the amorphous LaAlO3 (LAO) layer grown by the ALD process can generate 2-DEG (similar to 1 x 10(13)/cm(2)) with an electron mobility of 4-5 cm(2)/V.s. A much higher electron mobility was observed at lower temperatures. More remarkably, amorphous YAlO3 (YAO) and Al2O3 layers, which are not polar-perovskite-structured oxides, can create 2-DEG as well. 2-DEG was created by means of the important role of trimethylaluminum, Me3Al, as a reducing agent for STO during LAO and YAO ALD as well as the Al2O3 ALD process at 300 degrees C. The deposited oxide layer also plays an essential role as a catalyst that enables Me3Al to reduce the STO. The electrons were localized very near to the STO surface, and the source of carriers was explained based on the oxygen vacancies generated in the STO substrate.