High-Performance Thin-Film Transistors With Sputtered IGZO/Ga₂O₃ Heterojunction

Abstract

High-performance thin-film transistors (TFTs) with amorphous indium gallium zinc oxide (IGZO)/Ga2O3 heterojunction and the reference TFTs with single-layer IGZO, Ga2O3, and stacked IGZO/Al2O3 layers are fabricated by sputtering. The as-deposited IGZO/Ga2O3 TFT shows high ON current of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.97\,\,\mu \text{A}\cdot \mu \text{m}^{-{1}}$ </tex-math></inline-formula> at a drain voltage of 1 V, which is 7 orders of magnitude higher than that of the reference single layer TFTs and high mobility of 22.2 cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${}^{{2}}{\cdot }\text{V}^{-{1}}{\cdot }\text{s}^{-{1}}$ </tex-math></inline-formula> , which is twice of that of the reference as-deposited IGZO/Al2O3 TFT (11.5 cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${}^{{2}}{\cdot }\text{V}^{-{1}}{\cdot }\text{s}^{-{1}}$ </tex-math></inline-formula> ). Combining such superior conductivity of the IGZO/Ga2O3 TFT with the energy-level alignment, it indicates quasi-two-dimensional electron gas existed at the interface originated from the electrons confined in the potential well of IGZO. After annealing in air atmosphere, the IGZO/Ga2O3 TFT shows an effective gate modulation with high current ON/ OFF ratio of 1.2 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times \,\,10^{{7}}$ </tex-math></inline-formula> and high mobility of 15.8 cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${}^{{2}}{\cdot }\text{V}^{-{1}}\cdot \text{s}^{-{1}}$ </tex-math></inline-formula> comparing with that of the reference annealed IGZO/Al2O3 TFT (11.5 cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${}^{{2}}{\cdot }\text{V}^{-{1}}{\cdot }\text{s}^{-{1}}$ </tex-math></inline-formula> ). In addition, the bias stability of the annealed IGZO/Ga2O3 TFT is enhanced due to the interface passivation. Our results indicate that amorphous IGZO/Ga2O3 heterostructure is an effective way to achieve high-mobility and stable TFTs, which have great potential in low-cost, large-area, and flexible high-definition displays.