Mg x Zn1−x O Thin-Film Transistor-Based UV Photodetector with Enhanced Photoresponse

Abstract

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.

Investigation of UV photosensor properties of Al-doped SnO2 thin films deposited by sol-gel dip-coating method

“…The trap depth corresponding to different exponentials can be calculated by using the below equation [18] .…”

“…However, persistent photoconductivity and big recovery times are problematic characteristics due to deep traps [16] . Information about these traps levels can be obtained from the decay curve of photoconductivity after cutoff of excita-tion [17,18] .…”

“…7. It can be noticed that the curves are straight lines having a different slope with regard to different voltage according to the power law relation I V r , where r is the slope of different straight line segments [18,29] . In the absence of illumination (Fig.…”

Introductory Chapter: Photodetectors

“…Nevertheless, while a phototransistor is generally a few orders of magnitude more sensitive than the photodiode, the photoresponse speed is much slower. Polysilicon- [2], zinc oxide- [3], or organic polymer-based [4] thin film transistors (TFTs) have been adopted as photodetectors for optical interconnects, ultraviolet imaging and large area displays/flexible substrates, respectively. Schottky junction photodetectors include Schottky barrier photodiodes and metal-semiconductor-metal (MSM) photodiodes.…”

Magnesium Zinc Oxide Nanostructure-Modified Multifunctional Sensors for Full-Scale Dynamic Monitoring of Pseudomonas aeruginosa Biofilm Formation

“…A small amount of Mg can help suppress the oxygen vacancies benefit from stronger Mg-O bonding, and therefore MZO is used as an optimized channel material over ZnO for TFTs. MZO TFTs have been employed in a wide range of applications, such as photodetectors for UV lights, 7 converters/ inverters for building-integrated photovoltaics (BIPV), 8,9 and frequency modulators for SAW devices. 10 ZnO-and MZO-based nanostructures (ZnO nano and MZO nano ) are known to be functional and biocompatible nanostructures for biosensing applications.…”