Transparent Basic Logic Circuits with ITO-Stabilized ZnO Thin Film Transistors

Transparent basic logic circuits integrated by indium tin oxide(ITO)-stabilized ZnO thin film transistors(TFTs) are successfully fabricated on glass substrate. ITO-stabilized ZnO thin films with hybrid-phase microstructure are employed as active layers in the bottom-contact top-gated TFTs. We fabricate 13-stages ring oscillator (RO) with diode-load and pseudo-CMOS inverter respectively in order to tell the difference between those two schemes. The pseudo-CMOS RO exhibits 7V voltage swing and 42kHz oscillation frequency while the diode-load RO exhibiting 3.3V and 71kHz under the same supply voltage of 20V. Meanwhile, basic digital circuits like NOR gates and D flip flops with pseudo-CMOS scheme are also fabricated and they are logically correct. Those logic gates exhibit a typical high level of 4.3V, low level of 200mV and maximum operating frequency of nearly 10kHz under the 10V supply voltage. The transmittance of the chip is 80% to 90% in a 380-nm to 800-nm wavelength.