Channel mobility and contact resistance in scaled Zno thin-film

Zno thin-film transistors (TFTs) with scaled channel lengths of 10 μm, 5 μm, 4 μm, and 2 μm are fabricated by a top-down approach using remote plasma atomic layer deposition technique. Current-voltage measurements indicate an 푛-type channel enhancement mode transistor operation, with threshold voltages in the range of 8.4 V to 5.3 V, maximum drain currents of 4.6 μA/μm, 9.7 μA/μm, 19.4 μA/μm, and 24.7 μA/μm, and breakdown voltages of 80 V, 70 V, 62 V, and 59 V with respect to the channel lengths of 10 μm, 5 μm, 4 μm, and 2 μm. Contact resistance, effective electron mobility (including contact resistance) and channel electron mobility (excluding contact resistance) electron mobility extracted using the transmission line method (TLM) demonstrated a dependency on the channel length as a function of gate bias. The channel electron mobility for the 10 μm channel length TFT is 0.782 cm2/Vs (0.83 cm2/Vs) at a gate bias of 10 V (15 V) increasing to 8.9 cm2/Vs (19.04 cm2/Vs) when the channel length is scaled down to 2 μm. Finally, the contact sheet resistance of 4.6×105 Ω/sq extracted from measurements is 3.5× larger than the contact sheet resistance of 1.3×105 Ω/sq obtained from DFT calculation and 1D self-consistent Poisson-Shrödinger simulation showing an increase in the drive current