High-Performance Schottky-Barrier IGZO Thin-Film Transistors Based on Ohmic/Schottky Hybrid Contacts

In this work, we proposed and demonstrated etch-stopper-layer (ESL) structured indium-gallium-zinc oxide (IGZO) Schottky-barrier thin-film transistors (SBTFTs) with hybrid Ohmic/Schottky contacts utilizing single-layer Cu source/drain (S/D) electrodes. In this unique yet simple configuration, the AlOx layer deposited on the IGZO layer serves not only as a protection layer for the IGZO channel during S/D electrode etching but also as an interfacial layer for modulating the Schottky barrier of the Cu/IGZO contact. This, combined with quasi-Ohmic contact of Cu/IGZO, enables the formation of hybrid contacts based on a single-layer Cu electrode. The ESL-structured SBTFTs with hybrid contacts show a two-order magnitude increase in saturation current (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I}_{\text {dsat}}$ </tex-math></inline-formula>) compared to SBTFTs solely based on Schottky contacts, with high intrinsic gains exceeding 1500 at a gate voltage of 10 V, and good stability under gate bias and illumination stress. Utilizing technology computer-aided design (TCAD) simulation, the operation of ESL-structured IGZO SBTFTs was fully elucidated. Also, this study conducted a thorough investigation and analysis of the influence of source-drain gaps and Schottky contact lengths at the source on <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I}_{\text {dsat}}$ </tex-math></inline-formula> and saturation voltage (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\text {dsat}}$ </tex-math></inline-formula>) for the devices. This work provides a promising route to fabricate low-cost metal oxide SBTFTs with significantly increased <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I}_{\text {dsat}}$ </tex-math></inline-formula>.