Field-Effect Device Using Quasi-Two-Dimensional Electron Gas in Mass-Producible Atomic-Layer-Deposited Al2O3/TiO2 Ultrathin (<10 nm) Film Heterostructures

Abstract

We report the field-effect transistors using quasi-two-dimensional electron gas generated at an ultrathin (similar to 10 nm) Al2O3/TiO2 heterostructure interface grown via atomic layer deposition (ALD) on a SiO2/Si substrate without using a single crystal substrate. The 2DEG at the Al2O3/TiO2 interface originates from oxygen vacancies generated at the surface of the TiO2 bottom layer during ALD of the Al2O3 overlayer. High-density electrons (similar to 10(14) cm(-2)) are confined within a similar to 2.2 nm distance from the Al2O3/TiO2 interface, resulting in a high on-current of similar to 12 mu A/mu m. The ultrathin TiO2 bottom layer is easy to fully deplete, allowing an extremely low off-current, a high on/off current ratio over 10(8), and a low subthreshold swing of similar to 100 mV/decade. Via the implementation of ALD, a mature thin-film process can facilitate mass production as well as three-dimensional integration of the devices.