Articles you may be interested inHigh carrier mobility and electrical stability under negative bias illumination stress of ZnO thin-film transistors with N2O plasma treated HfOx gate dielectrics

We report a ZnO-based thin film transistor UV photodetector with a back gate configuration. The thin-film transistor (TFT) aspect ratio W/L is 150 lm/5 lm and has a current on-off ratio of 10 10. The detector shows UV-visible rejection ratio of 10 4 and cutoff wavelength of 376 nm. The device has low dark current of 5 Â 10 À14 A. The persistent photoconductivity is suppressed through oxygen plasma treatment of the channel surface which significantly reduces the density of oxygen vacancy confirmed by XPS measurements. The proper gate bias-control further reduces recovery time. The UV-TFT configuration is particularly suitable for making large-area imaging arrays. V

ZnO and its ternary alloy Mg x Zn 1Àx O (MZO) are promising wide-band-gap semiconductor materials well-suited to UV detection. The Mg content of MZO facilitates energy band gap engineering, enabling fabrication of UV photodetectors that can operate in the deep-UV region. Different types of UV photodetector based on ZnO have been reported, including photoconductive, Schottky, and transistor types. Transistor-based photodetectors have the advantage of being three-terminal devices, thus enabling biasing control and implementation in addressable arrays. In this paper we report an MZO thinfilm-transistor (TFT)-based UV photodetector. The device has a low dark current (2 9 10 À14 A) and an ON/OFF ratio of 10 11 . We show that by using a small amount of Mg (5%) in the MZO TFT we can substantially improve the photoresponse recovery time of the photodetector to 15 ms compared with 42 ms for a similar TFT with 0% Mg. We also observed a shift in the cutoff wavelength from 377.21 nm for the 0% Mg TFT photodetector down to 370.96 nm for the MZO TFT photodetector. We attribute the enhanced recovery time improvement of the MZO TFT UV photodetector to suppression of oxygen vacancies as a result of incorporation of the Mg in the MZO.