Effects of structure and oxygen flow rate on the photo-response of amorphous IGZO-based photodetector devices. (February 2018)

• Record Type: Journal Article
• Authors: Jang, Jun Tae; Ko, Daehyun; Choi, Sungju; Kang, Hara; Kim, Jae-Young; Yu, Hye Ri; Ahn, Geumho; Jung, Haesun; Rhee, Jihyun; Lee, Heesung; Choi, Sung-Jin; Kim, Dong Myong; Kim, Dae Hwan
• Is Part Of: Solid-state electronics. Volume 140(2018)
• Page Start: 115
• Page End: 121
• Publication Date: 2018-02
• Subjects: Amorphous-IGZO (a-IGZO) photodetector -- Structure dependence -- Oxygen flow rate (OFR) dependence -- Persistent-photoconductivity (PPC) -- Sub-gap density-of-states (DOS) -- Oxygen vacancy (VO) ionization -- Charge trapping -- Threshold voltage (VT) decomposition; Semiconductors -- Periodicals; Semiconducteurs -- Périodiques; 621.38152
• DOI: 10.1016/j.sse.2017.10.028
• Languages: English
• ISSNs: 0038-1101

Abstract

Highlights: Effect of structure and oxygen flow rate on photo-response in IGZO-based photodetector. Decomposition of persistent photoconductivity based on extracted sub-gap DOS. Quantitative analysis of photo-response including the PPC-eliminating technique. Abstract: In this study, we investigated how the structure and oxygen flow rate (OFR) during the sputter-deposition affects the photo-responses of amorphous indium-gallium-zinc-oxide (a-IGZO)-based photodetector devices. As the result of comparing three types of device structures with one another, which are a global Schottky diode, local Schottky diode, and thin-film transistor (TFT), the IGZO TFT with the gate pulse technique suppressing the persistent photoconductivity (PPC) is the most promising photodetector in terms of a high photo-sensitivity and uniform sensing characteristic. In order to analyze the IGZO TFT-based photodetectors more quantitatively, the time-evolution of sub-gap density-of-states (DOS) was directly observed under photo-illumination and consecutively during the PPC-compensating period with applying the gate pulse. It shows that the increased ionized oxygen vacancy (VO 2+ ) defects under photo-illumination was fully recovered by the positive gate pulse and even overcompensated by additional electron trapping. Based on experimentally extracted sub-gap DOS, the origin on PPC was successfully decomposed into the hole trapping and the VO ionization. Although the VO ionization is enhanced in lower OFR (O-poor) device, the PPC becomes more severe in high OFR (O-rich) device because the hole trapping dominates the PPC in IGZO TFT under photo-illumination rather than the VO ionization and more abundant holes are trapped into gate insulator and/or interface in O-rich TFTs. Similarly, the electron trapping during the PPC-compensating period with applying the positive gate pulse becomes more prominent in O-rich TFTs. It is attributed to more hole/electron traps in the gate insulator and/or interface, which is associated with oxygen interstitials, or originates from the ion bombardment-related lower quality gate oxide in O-rich devices.