AVS 58th Annual International Symposium and Exhibition
    Transparent Conductors and Printable Electronics Focus Topic Thursday Sessions
       Session TC+EM+NS-ThA

Paper TC+EM+NS-ThA10
Effects of Low-Temperature Annealing and Deep Traps in Operation Characteristics of Amorphous In-Ga-Zn-O Thin-Film Transistors

Thursday, November 3, 2011, 5:00 pm, Room 106

Session: Transparent / Printable Electronics Part 2
Presenter: Toshio Kamiya, Tokyo Institute of Technology, Japan
Authors: T. Kamiya, Tokyo Institute of Technology, Japan
Y. Kikuchi, Tokyo Institute of Technology, Japan
K. Ide, Tokyo Institute of Technology, Japan
K. Nomura, Tokyo Institute of Technology, Japan
H. Hosono, Tokyo Institute of Technology, Japan
Correspondent: Click to Email
Amorphous oxide semiconductors (AOSs) represented by a-In-Ga-Zn-O (a-IGZO) are expected for channel materials in thin-film transistors (TFTs) for next-generation flat-panel displays such as jumbo-size / fast / ultrahigh-resolution liquid-crystal displays and organic light-emitting diode displays. These are also expected for flexible electronics devices because they may be fabricated on unheated substrates, and thus produce flexible displays and circuits on inexpensive plastic substrates such as PET. On the other hand, it is known that, although room-temperature fabrication is possible for AOS TFTs, post-deposition thermal annealing at ≥300oC is better employed to obtain good stability. To employ this technology to the flexible electronics, the annealing temperature should be lowered to 200oC or far below. We reported that wet O2 annealing produces the best performance TFTs when annealed at ≥300oC, while it caused serious negative threshold voltage (Vth) shift at ≤200C. In this paper, we report the origin of the negative Vth shift by employing photoresponse spectroscopy of TFT characteristics. It revealed that the near-valence band maximum (VBM) states are reduced significantly even by the low-temperature 200C annealing, and implied that the negative Vth shift originates from free electrons released by annihilation of the near-VBM states.