AC Performance of Flexible Transparent InGaZnO Thin-Film Transistors and Circuits

Transparent transistors are mainly investigated in view of their integration in displays and their employment in wearable electronics where the integration of flexible and imperceptible systems is an important requirement. Here, the fabrication and ac performance of flexible InGaZnO thin-film transistors (TFTs) and circuits are presented to evaluate their suitability for analog sensor conditioning applications. Functional oxides are employed to guarantee the transparency of the device, while their fabrication processes are suitable to directly realize electronics on a flexible polyimide substrate. The TFTs show state-of-the-art performance with a field-effect mobility
$\mu _{\text {eff}}\,\,= {19}.{39}\,\, \text {cm}^{{2}} \text {V}^{-1} \text {s}^{-1}$
and functionality while bent to radii as low as 5 mm. Reliable scattering parameters measurements confirm transit frequencies as high as
$f_{t}~\approx ~7.84$
MHz. Simultaneously, nMOS ring oscillators (ROs) show functionality at supply voltage
${V} _{\text {DD}}$
ranging from 1.75 to 12.25 V with a maximum oscillation frequency
${f} _{\text {osc}}\,\,=132.9$
kHz. Finally, common-source amplifiers (CSAs) exhibit the voltage gains up to 10.7 dB, the cutoff frequencies up to 10.8 kHz, and a power consumption down to
$4.4~\mu \text{W}$
.