Localization of Gate Bias Induced Threshold Voltage Degradation in a-Si:H TFTs

Drain bias dependent bias temperature stress instability in a-Si:H TFT

“…Our result is in contrast with Ref. [17] which reports a higher reverse current than forward current. They argue that in the forward saturationmode, the defect region is fully inside the channel and the defect-free region (i.e., the pinch-off region of bias stress) lies in the pinch-off region and does not contribute to the current process, whereas in the reverse measurement, part of the defect region lies in the pinch-off region and the defect-free region is inside the channel and consequently the forward configuration has a lower saturation current than the reverse configuration.…”

Capacitance–voltage characteristics and device simulation of bias temperature stressed a-Si:H TFTs

“…We conclude that the N GA profile just before the pinch-off point should be close to the SQRT profile of Eq. (7). In other words, any SHE-enhanced defect states creation within this portion is negligible after the 100 s stress.…”

“…When a-Si:H TFT works as a constant current source to drive the organic light emitting diodes (OLED), the device operates in a saturation mode and thus experiences a drain bias-dependent bias temperature stress (V D -BTS). There were several recent papers concerning the threshold voltage (V t ) instability under a saturation mode V D -BTS [6][7][8][9]. A reduced V t -shift in a saturation mode V D -BTS, compared to the V tshift in a bias temperature stress with a zero drain bias (BTS), was interpreted as being controlled by the total gate charge [6].…”

Distribution of hydrogen in low temperature passivated amorphous silicon (a-Si:H) films from neutron reflectivity

“…One major limitation as related to a-Si:H is the processing temperature afforded by the relatively low thermal stability of most plastics; this has limited the maximum temperature in our previous work utilizing a-Si:H based transistor arrays on plastic substrates for display backplanes to less than 180°C [20]. However, this decreased temperature leads to an increased susceptibility of the a-Si:H to the threshold voltage shift during operation [21,22]. Thus, understanding the nature of the a-Si:H/hydrogenated silicon nitride gate insulator interface may be helpful in providing insight into routes to reduce this undesired effect.…”