Investigation of the Determining Factors for the “Mobility Boost” in High‐k‐Gated Transparent Oxide Semiconductor Thin‐Film Transistors

Abstract

AbstractIn metal‐oxide thin‐film transistors (TFTs), high‐k gate dielectrics often yield a higher electron mobility than SiO2. However, investigations regarding the mechanism of this high‐k “mobility boost” are relatively scarce. To explore this phenomenon, solution‐processed In2O3 TFTs are fabricated using eight different gate dielectrics (SiO2, Al2O3, ZrO2, HfO2, and bilayer SiO2/high‐k structures). With these structures, the total gate capacitance can be varied independently from the semiconductor–dielectric interface to study this mobility enhancement. It is shown that the mobility enhancement is a combination of the effects of areal gate capacitance and interface quality for disordered oxide semiconductor devices. The ZrO2‐gated TFTs achieve the highest mobility by inducing more accumulation charge with higher gate capacitance. Surprisingly, however, when the gate capacitance is held constant, no mobility enhancement is observed with the high‐k gate dielectrics compared to SiO2.