Characterization of High Mg Content MgZnO Ultraviolet Photodetectors with Noise Properties

Abstract

This study examined MgZnO thin films grown on quartz substrates using radio frequency magnetron sputtering. These films with varying Mg content were used to fabricate metal-semiconductor-metal (MSM) ultraviolet (UV) photodetectors (PDs). The best sample with optimized properties was obtained using a Mg content of 20%. The relatively high Mg content could effectively suppress the dark current to a value of the order of 10 −13 A. The PD exhibited an on-off ratio of seven orders of magnitude; its photo-responsivity increased with the increasing Mg content, which caused the suppression of the dark current. The UV-to-visible rejection ratio could be up to five orders of magnitude. Furthermore, the noise equivalent power (NEP) and the normalized detectivity (D * ) of the PD fabricated with 20% Mg were determined as 6.6 × 10 −15 W and 6.5 × 10 −14 cmHz 0.5 W −1 , respectively. These results indicate that an increase in the Mg content could reduce the dark current and the noise by effectively suppressing the donor-like defects.In recent years, ultraviolet (UV) photodetectors (PDs) have attracted considerable interest owing to their newly developed commercial applications in areas such as flame sensing, missile detection, and communications. 1 As an oxide semiconductor material exhibiting a continuous tunable wide bandgap from 3.37 eV to 7.8 eV, wurtzite MgZnO has demonstrated its versatile functionality in various device applications. 2,3 Thus, research into novel ZnO-related materials has increased. MgZnO is similar to aluminum gallium nitride (AlGaN); it is an ideal material for UV photodetectors due to its wide band-gap, high radiation hardness, and low growth temperatures. In addition, this material is abundant in nature, inexpensive, and eco-friendly. Moreover, Mg has a stronger affinity toward oxygen than to Zn in ZnO, which leads to a decrease in the number of zinc interstitials and oxygen vacancies owing to the higher ionic character of the Mg-O bonds than that of the Zn-O bonds (the fractional ionic character is 0.61 for ZnO and 0.84 for MgO). 4,5 The ionic radii of Mg 2+ and Zn 2+ are similar (Mg 2+ : 0.57 Å and Zn 2+ : 0.60 Å). It has been reported that the addition of Mg 2+ to Zn 2+ site did not cause significant lattice disorder, and films of Mg x Zn 1−x O could be deposited up to x = 0.33 without segregation of the MgO phase. 6 Such wide and tunable bandgap is expected to enable MgZnO-based UV photodetector to be applicable. Till now, MgZnO-based UV photodetectors have been fabricated using different methods, such as metal organic chemical vapor deposition (MOCVD), RF-sputtering, and molecular beam epitaxy (MBE). 7 MgZnO-based UV photodetectors have been fabricated with various types, such as PN junction, PIN Schottky barrier and MSM UV photodetector. 8-10 Furthermore, MSM photodetectors have several attractive features that make them ideal candidates for space applications, such as a low dark current, high responsivity, large bandwidth, and low noise densities. Solar or visible-blind MgZnO PDs have been fa...

Imaging ultra-weak UV light below 100 pW cm−2 using a 4H–SiC photodetector with an Al2O3 interfacial layer

“…[1][2][3][4][5][6][7] As is well known, the noise characteristics of a photodetector, including thermal noise, shot noise and 1/f noise, determine the weak light detection limit. 8,9 Achieving a low dark current is crucial for mitigating various sources of noise in a photodetector, thereby enhancing its ability to detect weak light with improved signal-to-noise ratios. [10][11][12] Compared to traditional semiconductors, wide bandgap semiconductors, such as SiC, AlGaN, ZnMgO, diamond, and Ga 2 O 3 , [13][14][15] have potential advantages in developing highly sensitive photodetectors for weak-light detection by virtue of their extremely low intrinsic carrier concentration and high physical stability along with chemical properties.…”

Amorphous Indium Titanium Zinc Oxide Thin Film Transistor and Impact of Gate Dielectrics on Its Photo-Electrical Properties

“…Magnesium (Mg), zirconium (Zr), aluminum (Al), and hafnium (Hf) are capable of being a carrier suppressor and regulating carrier concentration, facilitating stable operation of devices. [10][11][12] In addition to the foregoing, titanium (Ti) as a low-toxicity element with a lower standard electrode potential (−1.63 V) is a promising doping alternative but seldom studied. Considering future multifunctional optoelectronic applications, attempts to use InTiZnO as the active layer of TFT are highly expected.…”