Investigation of Intrinsic Electrical Characteristics and Contact Effects in p-Type Tin Monoxide Thin-Film...

We investigate the intrinsic electrical characteristics and source/drain parasitic resistance in p-type SnO TFTs fabricated using Ni electrodes based on the gated-four-probe method. Because of the relatively high work function and inexpensive price, Ni has been most frequently used as the source/drain electrode materials in p-type SnO TFTs. However, our experimental data shows that the width normalized parasitic resistances of SnO TFT with Ni electrodes are around one to three orders of magnitude higher than those in the representative n-type oxide TFT, amorphous indium- gallium-zinc oxide TFT, and are comparable with those in amorphous silicon TFTs with Mo electrodes. This result implies that the electrical performance of the short channel SnO TFT can be dominated by the source/drain parasitic resistances. The intrinsic field-effect mobility extracted without being influenced by source/drain parasitic resistance was ~2.0 cm2/Vs, which is around twice the extrinsic field-effect mobility obtained from the conventional transconductance method. The large contact resistance is believed to be mainly caused from the heterogeneous electronic energy-level mismatch between the SnO and Ni electrodes.