Low-temperature field-effect and magnetotransport properties in a ZnO based heterostructure with atomic-layer-deposited gate dielectric

A top-gate field-effect device with atomic-layer-deposited Al(2)O(3) dielectric was fabricated to investigate magnetotransport properties of two-dimensional electron gas (2DEG) at a semi-insulating ZnO-Mg(0.12)Zn(0.88)O double heterostructure grown by laser molecular-beam epitaxy. Hall mobility monotonically increased as the density of accumulated electrons increased. The highest mobility at 2 K was recorded to be 5000 cm(2) V(-1) s(-1) at a 2DEG density of 1.2x10(12) cm(-2), which is comparable to the previously reported value for a metallic ZnO/Mg(0.2)Zn(0.8)O heterostructure. Insulator-to-metal transition was observed at a critical density of 6x10(11) cm(-2). The metallic-state channel exhibited Shubnikov-de Haas oscillations, demonstrating an electric-field tunable quantum device based on transparent oxide semiconductor.