P‐141L: Late‐News Poster: Characterization of Physical Parameter‐Based Reliability on the Negative Bias Illumination Stress with Wavelength‐Dependence in Amorphous Silicon Thin‐Film Transistors

Abstract

We characterized the subgap density-of-states (DOS)-based reliability in hydrogenated amorphous silicon (a-Si:H) thin film transistors (TFTs). Physical origins of the negative bias illumination stress (NBIS)-induced threshold voltage shift (V T ) with wavelength-dependence are quantitatively and systematically investigated. As a result, the photon energy is closely related to a creation of subgap states and the rate of V OX (charge trapping into the gate insulator) /V T is determined by the relation between the photon energy and the band offset. Our methodology is expected to be very useful for the development of next generation large-area high performance active matrix liquid crystal display (AMLCD) technology.

Abnormal Behavior of Threshold Voltage Shift in Bias-Stressed a-Si:H Thin Film Transistor under Extremely High Intensity Illumination

“…Second, the dependence of incident light wavelength in NBTIS test on the abnormal threshold voltage shift was examined in order to find the cause of this behavior. If the electrons could be injected into the gate insulator under high intensity NBTIS, it is expected that the amount of injected electrons would be much higher in the wavelength of blue region (short wavelength) which has higher photon energy than that of red region (long wavelength) with relatively low photon energy. , Thus, two different wavelengths of light were injected respectively during high intensity NBTIS, and the resulting behavior was compared. As shown in Figure c, when the light corresponding to blue region with high photon energy was illuminated on the a-Si:H TFT under high intensity NBTIS, in most cases, the abnormal threshold voltage turnaround was observed.…”