Study on the electrical properties of ZnO thin film transistors using pyrochlore Bi_1.5Zn(_1+y)Nb_1.5O(_7+y) gate insulators fabricated by RF sputtering

A series of ZnO thin film transistors (TFTs) using pyrochlore Bi_1.5Zn(_1+y)Nb_1.5O(_7+y) (BZN) thin films as gate insulators by RF sputtering has been fabricated. The relations between the zinc content and performance of BZN thin films and ZnO-TFTs are studied. The electrical properties of the ZnO-TFTs with BZN gate insulators as a function of Zn content are discussed. The research results showed that excess Zn (5 mol.%) can significantly enhance the performance of BZN thin films and ZnO-TFTs, which is mainly attributed to the compensation of Zn volatility during fabrication of BZN thin films. At an applied electric field of 250 kV/cm, the leakage current density of BZN thin films with 5 mol.% excess Zn is approximately four order of magnitude lower than that of BZN thin films without excess Zn. The subthreshold and surface state density of ZnO-TFTs were decreased from 684 and 350 mV/dec to 4.5×1012 and 2×1012 cm-2, respectively, as Zn content was increased.