Positive Bias Illumination Stress Research Articles

Improvements in the bias illumination stability of amorphous InGaZnO thin-film transistors by using thermal treatments

The a-IGZO deposited by using the rf sputtering method features a conductive or an insulator characteristic based on amount of oxygen. We demonstrated that a post-treatment affects the resistance patterns of particular-sized InGaZnO(IGZO) thin films in a-IGZO thin-film transistors (TFTs). Post-annealing shifted the driving voltage of a-IGZO TFT to positive or negative values, depending on the annealing temperatures. Post-annealing may introduce oxygen vacancies or desorbed oxygen in the IGZO thin film. The changed driving voltage of IGZO TFTs coincides with the shift of the resistance pattern of IGZO. The fabricated a-IGZO TFTs exhibited a field effect mobility of 6.2 cm2/Vs, an excellent subthreshold gate swing of 0.32 V/decade, and a high I on/off ratio of > 109. Under positive bias illumination stress (PBIS) and negative bias illumination stress (NBIS), after 3,600 seconds, the device threshold voltage shifted about 0.2 V and 0.3 V, respectively.

Influences of Gate Bias and Light Stresses on Device Characteristics of High-Energy Electron-Beam-Irradiated Indium Gallium Zinc Oxide Based Thin Film Transistors

Under white light illumination, amorphous indium–gallium–zinc oxide (a-IGZO)-based thin-film transistors (TFTs) showed a large negative shift of threshold voltage of more than -15 V depending on the process conditions. We investigated the influences of both gate bias and white light illumination on device properties of IGZO-based TFTs untreated and treated with high-energy electron beam irradiation (HEEBI). The TFTs were treated with HEEBI in air at room temperature (RT), electron beam energy of 0.8 MeV, and a dose of 1×1014 electrons/cm2. The HEEBI-treated TFTs showed an improved stability under negative bias illumination stress (NBIS) and positive bias illumination stress (PBIS) compared with non-HEEBI-treated TFTs, suggesting that the acceptor-like defects might be generated by HEEBI treatment near the valence band edge.

Analyzing the effects of ambient dependence for InGaZnO TFTs under illuminated bias stress

Mechanism of the light-induced instability for InGaZnO thin film transistors has been investigated in this paper. The obvious ambient dependence under light illumination in vacuum and oxygen illustrates that the gas adsorption/desorption dominate the light-induced instability. Under illumination, the photo-generated holes would react with oxygen ions (O2−) and restore into oxygen molecules (O2) resulting in an apparent negative threshold voltage (Vt) shift. In order to verify the oxygen adsorption/desorption mechanism, the dark recovery characteristics were performed in vacuum and oxygen ambient follows 1000s light illumination and the fast recovery rate in oxygen ambient indicates that the oxygen molecules could be readsorpted. Furthermore, the instability of the gate bias stress under light illumination was investigated. For positive bias illumination stress (PBIS), the competition of the light-induced oxygen desorption and electron trapping mechanisms caused an unusual negative Vt shift comparing with gate bias stress in dark. On the contrary, the apparent Vt shift under negative bias illumination stress (NBIS) in different environments suggests that the light-induced oxygen adsorption will accelerate the degradation phenomenon.

The Effect of Oxide and Nitride Passivation on the Behavior of In-Ga-Zn-O Thin-Film Transistors under Negative and Positive Bias Illumination Stress: A Photo-excited Charge Collection Spectroscopic Analysis

The Effect of Oxide and Nitride Passivation on the Behavior of In-Ga-Zn-O Thin-Film Transistors under Negative and Positive Bias Illumination Stress: A Photo-excited Charge Collection Spectroscopic Analysis

Gate bias stress stability under light irradiation for indium zinc oxide thin-film transistors based on anodic aluminium oxide gate dielectrics

Thin-film transistors (TFTs) using indium zinc oxide as the active layer and anodic aluminium oxide (Al2O3) as the gate dielectric layer were fabricated. The device showed an electron mobility of as high as 10.1 cm2 V−1 s−1, an on/off current ratio of as high as ∼108, and a turn-on voltage (Von) of only −0.5 V. Furthermore, this kind of TFTs was very stable under positive bias illumination stress. However, when the device experienced negative bias illumination stress, the threshold voltage shifted to the positive direction. It was found that the instability under negative bias illumination stress (NBIS) was due to the electrons from the Al gate trapping into the Al2O3 dielectric when exposed to the illuminated light. Using a stacked structure of Al2O3/SiO2 dielectrics, the device became more stable under NBIS.

P‐41: Investigation of the Photon‐Enhanced Bias Instability of InGaZnO TFTs for the Application of Transparent AM‐OLED Displays

AbstractWe investigated the effect of the light‐induced bias instability of indium‐gallium‐zinc oxide(IGZO) thin film transistors. The IGZO TFT exhibited the excellent subthreshold gate swing of 0.12V/decade, Vth of −0.5V, and high Ion/off ratio of >109 as well as a high field‐effect mobility of 26.7 cm2/Vs. The Vth is not changed after positive bias illumination stress (PBIS) for 10000sec. However, the Vth is −8V after negative bias illumination stress (NBIS)for 10000sec. This phenomenon can be attributed the trapping of the photon‐induced charges into the gate dielectric/active interface. We fabricated transparent AM‐OLED driven by highly stable bottom gate IGZO TFT array