ABSTRACT
Thin film transistors (TFTs) made from amorphous or organic semiconductors are commonly used in the control circuits of large-area display electronics such as flat-panel TV screens. They can also be used in applications requiring flexible or nonplanar surfaces where the use of regular single crystal electronics is problematic. The usefulness of TFTs, however, has not been extended to high-performance applications due to significantly inferior electronic properties of thin films compared to their single crystal counterparts. For example, the field-effect electron mobility of amorphous Si is typically 0.1 cm2/V.s, whereas the mobility values in single crystal Si can be in excess of 1000 cm2/V.s [1]. Metal-oxide semiconductors based on Zn, In, Ga, and Hf have shown great promise in solving these problems for the current and next-generation flat-panel display electronics [2,3]. However, most metal-oxide semiconductor thin films are also amorphous and have limitations in current density and switching on/off ratios. Although they offer higher electron mobilities than amorphous Si films and therefore show promise in higher-speed circuit applications [4], they are not yet suitable for high-performance digital or analog circuits beyond display control electronics.
