Illumination instability analysis of ZnO thin film transistors with HfO2 gate dielectrics

ZnO thin film electronics have received much attention due to the relatively high electron mobility of ZnO thin films in comparison to amorphous silicon (a-Si) and organic thin films. There is significant interest in using ZnO thin film transistors (TFTs), or similar oxides such as InGaZnO and zinc tin oxide, to replace a-Si TFTs in large area display technologies such as active matrix liquid crystal display (AMLCD) devices and active matrix organic light-emitting diode (AMOLED) displays where transparency in the visible range and high carrier mobilities are significant advantages. In addition, the integration of high dielectric constant (high-k) dielectrics in ZnO TFTs has demonstrated performance advantages including reduced operating voltage, increased I_on/I_off ratios, and larger transconductance. HfO₂ has emerged as a high-k dielectric of choice for both silicon microelectronics and thin film electronics due to the high dielectric constant (ε_r ~ 25ε₀), low leakage current, and low synthesis temperature.