Enhancing electrical characteristics of ALD-deposited SnO2 thin-film transistors via controlling ozone concentration and Al supercycle doping

초록

Tin dioxide (SnO2) is a promising oxide semiconductor for low-power electronics, but its intrinsically high carrier concentration from oxygen vacancies limits its performance in thin-film transistors (TFTs). In this study, we present a systematic approach to optimize SnO2 TFTs deposited by atomic layer deposition (ALD) at a low temperature of 150 °C. We first optimized film quality by controlling ozone concentration and dosing time, which successfully reduced oxygen vacancy content. To further suppress the high carrier concentration, we employed a supercycle ALD method to dope aluminum (Al) as an acceptor. Through Hall measurements, we confirmed that a moderate Al doping level (5-cycle) effectively reduced the carrier concentration from 2.72 × 1021 cm-3 to 4.47 × 1019 cm-3while preserving hall mobility. Subsequent TEM-EDS analysis confirmed that the Al atoms were successfully incorporated into the SnO2 matrix as dopants without forming a distinct interlayer. The impact of ozone concentration and Al doping on electrical characteristics was verified through the fabrication of thin-film transistors (TFTs), followed by channel thickness optimization to ensure effective channel modulation. Consequently, the optimized device featuring a 5-nm-thick, 5-cycle Al-doped channel provided the best device performance, achieving a high on/off current ratio of approximately 3.94 × 106 and a field effect mobility of approximately 8.96 cm2/V·s. These results highlight that precise control of the ALD process parameters (ozone concentration and Al doping) enables effective carrier-density suppression and performance optimization in ultra-thin SnO2 TFT channels.

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