Multi-Layer MoS2 FET with Small Hysteresis by Using Atomic Layer Deposition Al2O3 as Gate Insulator

Abstract

The speed of integrated circuits has become one of the key technical concerns in order to be able to improve the performance of microelectronics devices. A complex device structure and high cost process technology are required in order to increase the clock speed of a functional circuit built with conventional Sifield effect transistors (FETs), and the low electron mobility of amorphous Si (∼ 1c m 2 /V s) is undesirable for some applications in large area electronics. For example, the low mobility is a bottleneck that prevents fabricating active matrix liquid crystal displays (AMLCD) with high resolutions and high driving speeds. 1 Two-dimensionalmaterials,suchasgraphene,maybeabletoovercome some of the shortcomings presented by Si materials. Graphene has mobility on the order of 10,000 cm 2 /V ·s, but another property inherent to graphene is its zero band-gap, which introduces many technical challenges to realize reliable, high-performance devices. 2 Semiconducting transitional metal dichalcogenides (TMDs), such as molybdenum disulfide (MoS2), are two-dimensional materials similar to graphene, and they are considered to be potential replacement for amorphous Si. In MoS2, Mo and S atoms are strongly bonded with covalent bonds within each layer, while interlayer bonding is maintained via weak Van der Waals interactions. 3 In addition, MoS2 has a sizable band-gap, with an indirect band-gap of 1.2 eV for bulk material and a direct band-gap of 1.8 eV for a single-layer configuration. 3 This property of MoS2 leads to a low off-current when a MoS2 FET is fabricated. 4