In the present work, we report the high performance of zinc oxide (ZnO) nanosheet (NS) based source-gated transistors (SGTs) with asymmetric Schottky source and ohmic drain contacts: low saturation drain-source voltages (~2V) in the output scans (even at high gate voltages), high current on/off ratio (>107) and low off-currents (0.1pA). For a deeper understanding of the device mechanism and charge transport at metal–semiconductor contact interface, temperature dependent current–voltage studies have been performed. They revealed that the device operation can be ascribed to 3 main processes: i) the reverse biased Schottky source contact, which essentially controls charge carrier injection in to the NS channel, ii) effective manipulation of the source barrier by the gate field and iii) modulation of the depletion region beneath the source contact. These results are likely to improve the future generations of the ZnO based SGTs which offer several advantages for thin-film transistor design, including low power dissipation, small signal amplification, and as active load for the electronic circuits. •Single-crystalline ZnO Nanosheets on r-plane Saphire•High performance FET using single ZnO Nanosheet (Mobility=50cm2/Vs)•High performance source-gated transistors: low saturation voltages (~2VD)•Low temperature processes for the device fabrication