Effect of Mechanical Strain on Hydrogenated Amorphous Silicon Thin-Film Transistors and Compensation Circuits on Flexible Substrates

Hydrogenated amorphous silicon (a-Si:H) thin-film transistor (TFT) compensation pixel circuits were fabricated on polyethylene naphthalate substrates at a maximum temperature of 170 °C. The typical a-Si:H TFTs showed a field-effect mobility (μ
_FE
) of 0.8-1.1 cm
²
/Vs, a threshold voltage (V
_T
) of 2-3.3 V, a subthreshold swing (SS) of ~0.65 V/decade, and an ON/OFF current ratio of 10
⁷
-10
⁸
. Under DC gate-bias stress without compensation, the TFT drive current decreased by ~50% without mechanical strain and ~60% with applied tensile strain. The TFT circuits effectively compensated for the change in the TFT drive current to within 10% of the original drive current value under mechanically strained and unstrained states. The orientation of the TFT within the circuit was found to affect the circuit compensation; TFTs having a channel length perpendicular to the mechanical strain were found to have a 50% higher threshold voltage shift (ΔV
_T
) compared to devices parallel to the applied strain.