Underlayer Selection to Improve the Performance of Polycrystalline Ge Thin Film Transistors

Abstract

We fabricated accumulation-mode metal source/drain p-channel thin film transistors using solid-phase crystallized Ge with different thickness formed on glass substrate. By thinning the Ge layer with the largest grain size (3.7 μm), the channel region got fully-depleted, and the TFT exhibited both high on/off current ratio (~102) and field effect mobility (170 cm2 V-1 s-1). We prepared interfacial layers (GeO2 and Al2O3) between Ge and the substrate to achieve a high Hall hole mobility with a thin film, which is the key for improving TFT characteristics. As a result, inserting Al2O3 underlayer improved the electrical properties of thin Ge (50 nm) layers.