We successfully fabricated high-performance Al-Sn-Zn-O thin-film transistors (ATZO TFTs) with a quasidouble-channel (QDC) structure on glass by radio-frequency magnetron sputtering. The bilayer ATZO films are fabricated with different oxygen partial pressures during the sputtering process. The structure of the top ATZO layer is optimized to improve OFF-state performances. With this QDC structure, the ATZO TFT demonstrates excellent electrical performances, including a low OFF-state current of 840 fA, an ON/ OFF current ratio of 1.08 × 10 9 , a steep threshold swing of 0.16 V/decade, a superior saturation mobility of 108.28 cm 2 V −1 s −1 , and a threshold voltage of 2.09 V.Index Terms-High-performance, Al-Sn-Zn-O (ATZO), thinfilm transistor (TFT), quasi-double-channel (QDC) structure.
In this work, fully transparent dual-layer channel amorphous indium gallium zinc oxide thin-film transistors (a-IGZO TFTs) are fabricated on glass substrates at low temperature. Dual-layer channel a-IGZO TFTs are studied by changing the partial pressure of oxygen while sputtering IGZO layers for comparison with single-layer channel TFTs which are fabricated with a constant oxygen content. All four types of dual-layer channel TFT sample demonstrate better performance, on-to-off ratios of ∼108 and low subthreshold swing (SS) of less than 200 mV/decade, than the single-layer ones. TFTs with two layers, a low-oxygen layer and a high-oxygen layer formed using oxygen partial pressures of 0.01 and 0.05 Pa, respectively demonstrate relatively better performance with a mobility of more than 60 cm2 V−1 s−1. Among them, the TFTs with a channel layer thickness ratio of 3 : 1 show the best transfer characteristics with a high on-to-off current ratio (I
on/off) of 1.8 × 108 and a low SS of 135 mV/decade.
In this work, fully transparent high performance double-channel indium-tin-oxide/Al–Sn–Zn–O thin-film transistors (ITO/ATZO TFTs) are successfully fabricated on glass by radio frequency (RF) magnetron sputtering. The ITO layer acts as the bottom channel layer to increase the channel carrier concentration. The top ATZO channel layer, which is deposited via high oxygen partial pressure in the sputtering process, is useful to control the minimum off-state current. After annealing, the ITO/ATZO TFT demonstrates outstanding electrical performances, including a high ON/OFF current ratio (Ion/Ioff) of 3.5 × 108, a steep threshold swing (SS) of 142.2 mV/decade, a superior saturation mobility (μsat) of 246.0 cm2/Vs, and a threshold voltage VT of 0.5 V. The operation mechanisms for double-channel structures are also clarified.
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