Sputter-Deposited copper iodide thin film transistors with low Operating voltage

This paper reports on a back-gated p-type thin film transistor (TFT) with copper iodide (CuI) as the channel material, a HfO2 gate dielectric layer, and Al2O3 passivation. The gamma-CuI channel was deposited from a CuI target using DC magnetron sputtering at room temperature. Our TFT can be fully shut off by VG = 4 V, with a fieldeffect channel hole mobility mu h 1.5-2 cm2 V- 1 s- 1. An anneal in forming gas was performed twice, once at 200 degrees C, then at 250 degrees C to improve gate control, yielding a final Ion/Ioff current ratio of 250. The anneal served two purposes: to reduce the oxygen acceptor density in the CuI channel and reduce the concentration of interface states between the CuI, Al2O3 passivation, and HfO2. A model of the device was built in an industrial TCAD simulator, which reproduces the measured characteristics and allows an estimation of interface state densities and channel doping.