Metal-Semiconductor Field-Effect Transistor Made Using Amorphous In-Ga-Zn-O Channel and Bottom Pt Schottky Contact Structure at 200 C

Amorphous In-Ga-Zn-O (a-IGZO) based metal-semiconductor field-effect transistors (MESFETs) were fabricated at 200°C. A bottom Pt structure was employed to form a good Schottky gate, and channel thickness was optimized to 230 nm to obtain high on-currents I on > 10 −6 A, on-to-off current ratios > 10 6 and low subthreshold voltage swing of 129 mV/decade. The field-effect mobility ( μ FE ) was as small as 0.5 cm 2 (Vs) −1 , which is explained quantitatively by the subgap trap density in the 200°C-annealed a-IGZO. The present result suggests that a double-layered channel with different donor densities will be effective to improve I on and μ FE of a-IGZO MESFETs.