High-Gain Transparent Inverters Based on Deuterated ZnO TFTs Fabricated by Atomic Layer Deposition

Three types of highly transparent inverter circuits, enhancement/depletion, pseudo-CMOS and feedback structures, are fabricated by using zinc-oxide thin film transistors (TFTs) with deuterium plasma immersion to adjust the threshold voltage of the depletion-mode TFTs. Their DC and AC performance are investigated and compared systematically. Especially, the feedback structure inverters demonstrate a maximum gain of -310V/V at V
_DD
= 10 V, which is the highest DC gain ever to be reported for oxide TFTs. Furthermore, the frequency responses of these three inverter types are examined, showing a maximum AC gain of 210 V/V at a 10 mV amplitude input in the pseudo-CMOS inverters. These high-gain transparent inverters have great potential to be used as the common-source amplifiers in the measurement of photo-stimulated electroencephalogram signals.