Abstract
Herein, we investigated the effects of active layer thickness (tS) on the electrical characteristics and stability of high-mobility indium–gallium–tin oxide (IGTO) thin-film transistors (TFTs). IGTO TFTs, with tS values of 7 nm, 15 nm, 25 nm, 35 nm, and 50 nm, were prepared for this analysis. The drain current was only slightly modulated by the gate-to-source voltage, in the case of the IGTO TFT with tS = 50 nm. Under positive bias stress (PBS), the electrical stability of the IGTO TFTs with a tS less than 35 nm improved as the tS increased. However, the negative bias illumination stress (NBIS) stability of these IGTO TFTs deteriorated as the tS increased. To explain these phenomena, we compared the O1s spectra of IGTO thin films with different tS values, acquired using X-ray photoelectron spectroscopy. The characterization results revealed that the better PBS stability, and the low NBIS stability, of the IGTO TFTs with thicker active layers were mainly due to a decrease in the number of hydroxyl groups and an increase in the number of oxygen vacancies in the IGTO thin films with an increase in tS, respectively. Among the IGTO TFTs with different tS, the IGTO TFT with a 15-nm thick active layer exhibited the best electrical characteristics with a field-effect mobility (µFE) of 26.5 cm2/V·s, a subthreshold swing (SS) of 0.16 V/dec, and a threshold voltage (VTH) of 0.3 V. Moreover, the device exhibited robust stability under PBS (ΔVTH = 0.9 V) and NBIS (ΔVTH = −1.87 V).
Highlights
Published: 28 May 2021Amorphous indium–gallium–zinc oxide (IGZO) thin-film transistors (TFTs) were reported for the first time by Nomura et al in 2004; since, they have attracted significant attention because of their excellent electrical properties, low process temperature, large-area uniformity, and low fabrication cost [1,2,3,4,5]
We examined the effects of tS on the transfer characteristics and stability of high-mobility amorphous indium–gallium–tin oxide (IGTO) TFTs with tS values of 7, 15, 25, 35, and 50 nm
The obtained results showed that with an increase in tS, V TH shifted in the negative direction, and the subthreshold swing (SS) and μFE of the fabricated IGTO TFTs increased
Summary
Published: 28 May 2021Amorphous indium–gallium–zinc oxide (IGZO) thin-film transistors (TFTs) were reported for the first time by Nomura et al in 2004; since, they have attracted significant attention because of their excellent electrical properties, low process temperature, large-area uniformity, and low fabrication cost [1,2,3,4,5]. IGZO TFTs are being widely used as a backplane for large-area active-matrix flat-panel displays, such as organic light-emitting diode (OLED) displays and liquid-crystal displays (LCD) [6,7,8]. The relatively low field-effect mobility of IGZO TFTs (μFE = ~10 cm2 /V·s) still hinders their application in the backplane of ultra-high-resolution and high-frame-rate displays [9,10]. This is because the OLED pixels require a high current to emit light. IGTO has recently attracted considerable attention as a promising active material for nextgeneration high-mobility oxide TFTs. The In3+ and Sn4+ ions have almost similar electronic
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