title: Photobias instability of high performance solution processed amorphous zinc tin oxide transistors.
abstract: The effects of the annealing temperature on the structural and chemical properties of soluble-processed zinc-tin-oxide (ZTO) films were examined by transmission electron microscopy, atomic force microscopy, high resolution X-ray reflectivity, and X-ray photoelectron spectroscopy. The density and purity of the resulting ZTO channel layer increased with increasing annealing temperature, whereas the oxygen vacancy defect density decreased. As a result, the device performance of soluble ZTO thin film transistors (TFTs) was improved at higher annealing temperature. Although the 300 °C-annealed ZTO TFT showed a marginal field-effect mobility (μFE) and high threshold voltage (Vth) of 0.1 cm(2)/(V s) and 7.3 V, respectively, the 500 °C-annealed device exhibited a reasonably high μFE, low subthreshold gate swing (SS), Vth, and Ion/off of 6.0 cm(2)/(V s), 0.28 V/decade, 0.58 V, and 4.0 × 10(7), respectively. The effects of dark negative bias stress (NBS) and negative bias illumination stress (NBIS) on the degradation of transfer characteristics of ZTO TFTs were also investigated. The instability of Vth values of the ZTO TFTs under NBS and NBIS conditions was suppressed with increasing annealing temperature. To better understand the charge trapping mechanism, the dynamics of Vth shift with NBS and NBIS time for all ZTO TFTs was analyzed on the basis of the stretched exponential relaxation. The negative Vth shift for each transistor was accelerated under NBIS conditions compared to NBS, which resulted in a higher dispersion parameter and smaller relaxation time for NBIS degradation. The relaxation time for NBS and NBIS instability increased with increasing annealing temperature, which is discussed on the basis of the transition mechanism of oxygen vacancy defects.
authors.affiliation: Department of Materials Science and Engineering, WCU Hybrid Materials Program, and Inter-university Semiconductor Research Center, Seoul National University, Seoul 151-742, Republic of Korea.
authors.forename: Yoon Jang
authors.initials: YJ
authors.lastname: Kim
authors.forename: Bong Seob
authors.initials: BS
authors.lastname: Yang
authors.forename: Seungha
authors.initials: S
authors.lastname: Oh
authors.forename: Sang Jin
authors.initials: SJ
authors.lastname: Han
authors.forename: Hong Woo
authors.initials: HW
authors.lastname: Lee
authors.forename: Jaeyeong
authors.initials: J
authors.lastname: Heo
authors.forename: Jae Kyeong
authors.initials: JK
authors.lastname: Jeong
authors.forename: Hyeong Joon
authors.initials: HJ
authors.lastname: Kim