Ultrathin amorphous ZnGexSnO films for high performance ultra-thin-film transistors

Ultrathin amorphous ZnSnO (a-ZTO) films and ultrathin amorphous ZnGeSnO (a-ZGTO) films with various Ge contents were deposited by pulsed laser deposition for ultra-thin-film transistors (UTFTs). The thicknesses of the channel layers are approximately 3.2 nm. The properties of these ultrathin films and behaviors of these UTFTs were comparatively studied in detail. The a-ZTO ultrathin film exhibited a low concentration of the oxygen vacancy (VO) compared to a-ZGTO ultrathin films. Among all the UTFTs, the a-ZTO UTFT demonstrated the undoubtedly best performance with an on/off current ratio of more than 107, the largest field-effect mobility of 23.2 cm2 V−1 s−1, a positive threshold voltage of 2.0 V, a very small subthreshold swing of 0.31 V/decade, and the best long-term stability under bias stress, suggesting that the introduction of VO suppressors is dispensable with such a small thickness. Above all, the concentration of the oxygen vacancy is easily controlled in the ultrathin a-ZTO nanofilms, leading to the UTFTs operating in the enhancement mode with a high field-effect mobility of 23.2 cm2 V−1 s−1 and excellent long-term stability. The a-ZTO ultrathin film and ultra-thin-film transistor are very potential for future electrical applications with their excellent properties.