P‐1.17: Ultraviolet Light Response of Amorphous Oxide Thin‐Film Transistors with Double‐Stacked Channel Layers

Abstract

We investigated the ultraviolet (UV) light detectors of amorphous InGaZnO thin film transistors (a-IGZO TFTs) with doublestacked channel layers (DSCL). When the UV light wavelength decreased from 400 nm to 370 nm, the devices with DSCL exhibited better light response properties than those with single channel layers. Especially, the a-IGZO TFT with DSCL (OR-IGZO/OD-IGZO) structure achieved 28.6 dB of sensitivity, 9.7×10 -7 A/W of responsivity, and 1.6×10 8 cm•Hz 0.5 •W -1 of detectivity under the UV light with wavelength = 370 nm. This improvement was assumed to the best combination of light absorption and interface states for the special DSCL structure.

Amorphous InGaZnO Thin-Film Transistors with Double-Stacked Channel Layers for Ultraviolet Light Detection

“…In order to quantitatively study the sensing properties of the DSCL-TFTs, we defined some useful terms, i.e., net photogenerated current (I photo ), sensitivity (S), responsivity (R), and detectivity (D*) [4,18]. I photo was defined as follows:…”

“…detection [18]. However, the detailed design methods as well as the related physical essence are still unknown for a-IGZO TFTs with DSCL (DSCL-TFTs) UV light detectors.…”

“…Recently, we proposed to use double-stacked channel layers (DSCL) to increase the detecting abilities of a-IGZO TFT UV sensors, resulting in a good sensitivity of 28.6 dB when they were illuminated by 370 nm UV light [18]. In contrast to the optimized DSCL structure for general-purpose TFT devices [19], the best DSCL deposition consequence of oxygen-rich (OR) IGZO followed by oxygen-deficient (OD) IGZO was proven for UV light detection [18]. However, the detailed design methods as well as the related physical essence are still unknown for a-IGZO TFTs with DSCL (DSCL-TFTs) UV light detectors.…”

17‐1: Persistent Photoconductivity Suppression in Amorphous Oxide Thin‐Film Transistors with Double‐Stacked Channel Layers

“…In other words, the electron concentration in the OD layer is greater than that in the OR layer. Accordingly, the diffusion of electrons from OD to OR takes place (9). At the same time, because the applied voltage of the gate is negative, the electrons will move towards OD, and when the diffusion and applied voltage reach equilibrium, a built-in electric field (Vbuild-in) is formed at the interface, and hence the electrons will accumulate at the interface, forming a conductive sub-channel, as shown in Figure 5(b).…”

“…Various methods have been proposed to address this issue, including the gated three-terminal device architecture, positive gate bias pulse, and so on (6)(7)(8). On the other side, the double-stacked channel layers (DSCL), which consist of oxygen-rich (OR) and oxygen-deficient (OD) oxide semiconductor films, have been proposed to enhance the corresponding TFT devices' electrical performance, bias-stress stability, and even responsivity and sensitivity to UV light by our group and the other researchers (9,10). However, the influence of DSCL on the persistent photoconductivity as well as the related addressing methods are still unknown.…”