| 초록 |
Amorphous oxide semiconductors (AOSs) are a promising active layer for transparent, flexible thin film transistors. (TFTs) Solution processing for the formation of AOS layers is likely a viable alternative to vacuum deposition techniques with respect to processing temperature and cost, as well as having direct-write capabilities, such as in inkjet printing. However, solution-processed AOS TFTs suffer from severe bias-stress instability for device operation due to inherently rich and undefined defect states, thus inhibiting reproducible, reliable performance. Here, we report on the generation of solution-processed gallium tin zinc oxide (GSZO) TFTs that exhibit superior stability against electrical stress during device operation under ambient conditions. We compared GSZO with gallium-free tin-doped ZnO (ZTO) layers, and we suggest that oxygen vacancies and the control of them are a key to producing reproducible AOS channel layers by solution processing. We generated solution-processed AOS TFTs using GSZO layers as the channel. GSZO transistor has good electrical performance similar with ZTO. This device exhibit the saturation mobilities of 1.0 to 1.2 cm−2 V−1 s−1, the on/off current ratios of ~106 and the subthreshold slope of 1.5 V dec-1 and threshold gate voltage was positive (Vth = 3V). Importantly, these AOS TFTs had excellent bias-stress stability during device operation under ambient conditions. The cause of the bias-stress stability was investigated by comparing GSZO and ZTO layers. The creation and quantity of oxygen vacancies generated from the addition of Ga ions were probed with concrete spectroscopic results. By photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS), we observed a general trend toward suppression of oxygen-related defects upon the addition of Ga. Electron paramagnetic resonance (EPR) of both the GSZO and ZTO layers allowed us to quantify the oxygen vacancies. Due to the reproducible TFT characteristics, the strategy presented here will enable the development of solution-processable high-performance electronic devices for transparent, flexible substrates |
