Source–drain contact impacts on electrical performances and low frequency noise of InZnO thin-film transistors down to 7 K

Abstract

Source–drain contacts seriously affect low frequency noise (LFN) in amorphous IZO (a-IZO) thin-film transistors with bilayer ITO/Mo electrodes at cryogenic temperatures. In the range of 7–300 K, electrical and LFN performances of devices are measured, and the temperature dependence of channel resistances (Rch) and contact resistances (Rsd) is also analyzed. The carrier transport transition both occurs in a-IZO channels at 80 K and in ITO/Mo electrodes at 100 K, which causes the variation in Rsd and Rch. Below 80 K, the variable range hopping conduction dominates in the channels and contacts with Rsd/Rch ratio > 1. The LFN measured results indicate that the noise is contact-dominated. At higher temperatures above 120 K, the band conduction dominates in the channel, with Rsd/Rch ratio < 1, and the noise is channel-dominated. The main mechanism of noise transfers from the mobility fluctuation to the carrier number fluctuation. We consider that the contribution of contact noise to total LFN is determined by the Rsd/Rch ratio. This work provides comments for the selection of electrode materials in devices applied to cryogenic integration circuits.