Transparent ring oscillator based on indium gallium oxide thin-film transistors

Highly transparent ring oscillators, exhibiting ∼75% optical transmittance in the visible portion of the electromagnetic spectrum, are fabricated using indium gallium oxide as the active channel material and standard photolithography techniques. The n-channel indium gallium oxide transparent thin-film transistors (TTFTs) exhibit a peak incremental mobility of ∼7 cm2 V−1 s−1 and turn-on voltage of ∼2 V. A five-stage ring oscillator circuit (which does not employ level-shifting) exhibits an oscillation frequency of ∼2.2 kHz when the gate and drain of the load transistor are biased at 30 V; the maximum oscillation frequency observed is ∼9.5 kHz, with the gate and drain of the load transistor biased at ∼80 V.