Effect of Tensile and Compressive Bending Stress on Electrical Performance of Flexible a-IGZO TFTs

We report the changes in device performance of flexible amorphous indium-gallium-zinc-oxide thin-film transistors (TFTs) by 1.65% tensile or compressive bending stress for 10 k times. The TFTs exhibit negative threshold voltage (ΔV
_Th
) shift and enhanced drain current (I
_D
). TFT performance under repetitive tensile bending stress exhibits comparatively large threshold voltage shift (ΔV
_Th
= -2.3 V) than compressive bending stress (ΔV
_Th
= -0.9 V), which might be originated from both the generation of interface states (Nint) and gap trap density (dN
_gap
/dE) by 3.5 × 10
¹¹
/cm
²
and 5.7 × 10
¹²
/cm
²
eV, respectively under tensile bending stress. These are much higher than those (N
_int
: 1.2 × 10
¹¹
/cm
²
and dN
_gap
/dE: 2.2 × 10
¹²
/cm
²
eV) for compressive bending. The increase in the DOS appears after both types of the bending stress which is related to the generation of oxygen vacancies. According to technology computer aided design simulation, the 10 k times repetitive compressive bending stress generates donor like states (ΔN
_GD
) ~ 2 × 10
¹⁶
cm
^-3
and tensile bending stress generates ΔN
_GD
~ 9.5 × 10
¹⁶
cm
^-3
at ~E C - 0.35 eV.