The asymmetrical degradation behavior on drain bias stress under illumination for InGaZnO thin film transistors

Abstract

This paper investigates behavior of drain bias stress and gate-drain bias stress under illumination for InGaZnO thin film transistors as the current-driver operated. Properties exhibit two-stage degradation behavior during drain bias stress. The photo-excited hole non-uniform trapping from illumination induces drain side barrier lowering and causes an apparent hump phenomenon of the subthreshold swing. However, the positive threshold voltage shift without a hump phenomenon after gate-drain bias stress is different degradation behaviors. It is reliant on whether or not an inversion layer exists in the channel. This work also employs capacitance-voltage measurement to further clarify the mechanism of degradation behaviors.

Modulation of optical and electrical properties of sputtering-derived amorphous InGaZnO thin films by oxygen partial pressure

“…InGaZnO 4 (IGZO) is a kind of transparent and amorphous oxide semiconductor which is made of ZnO [8], doped with In 2 O 3 and Ga 2 O 3 [9][10][11]. IGZO thin films are expected to become active layer materials of TFTs for the next generation display technology due to its good electrical properties, high mobility in low-temperature process, sedimentary characteristics and optical properties, which are important requirements for flat-panel display applications [1,10,12,13].…”

Suppression of Degradation Induced by Negative Gate Bias and Illumination Stress in Amorphous InGaZnO Thin-Film Transistors by Applying Negative Drain Bias

“…In particular, degradation under negative gate bias and illumination stress (NBIS) has been recognized as a crucial issue of oxide TFTs. This is because the TFTs in AM-LCDs and AM-OLEDs are frequently negatively biased and exposed to backlight or ambient light during operation. − Until now, three possible mechanisms have been proposed for NBIS degradation: photogenerated hole trapping in the gate insulator (GI) or at the GI/semiconductor interface, − defect creation in the active layer, − and donor-like defect creation combined with a buildup of positive charge at the GI/active layer interface . The stability of oxide TFTs under long-term current operation is also an important issue for pixel signal level and emission intensity in current-driven AM-OLEDs. , However, the degradation of amorphous oxide TFTs under a combination of NBIS and drain bias ( V DS ) has been rarely reported.…”

Exploring the photoleakage current and photoinduced negative bias instability in amorphous InGaZnO thin-film transistors with various active layer thicknesses

“…This is due to the fact that the electrons are excited from the trapped states existing near the valence band ( E V ). In addition, the a-IGZO TFTs inevitably suffer electrical and optical stresses during practical operation conditions, especially for the negative bias and illumination stress (NBIS) tests [11–16], which leads to device instability and restricts the development of oxide TFTs for commercial products.…”