Modulating Electrical Characteristics of ZnO Thin-Film Transistors by Scaling Down Gate Dielectric Thickness

Modulating electrical characteristics of zinc oxide (ZnO) thin-film transistors (TFTs) through gate dielectric thickness is expected to compensate for short-channel effects (SCEs) for driving Micro-LEDs. Here, we first design the ZnO TFTs with thinner dielectric to relieve threshold voltage (V-TH) roll-off and subthreshold swing (SS) degradation as the channel length scales down to a few micrometers. The proposed compensation method was then demonstrated and verified by fabricating ZnO TFTs with various gate dielectric thicknesses. The VTH roll-off and SS degradation can be avoided, and ION/IOFF ratio can be improved by an order of magnitude, which is of particular interest for shorter channel ZnO TFTs. By solving the current density equation, it has been found that a higher electric field and a higher current density form near ZnO/Al2O3 interface when the gate dielectric thickness decreases. Moreover, the first-principle calculations reveal that localization of transmission eigenstates at the semiconductor-insulation interface with thinner dielectric layer provides a better conductive channel for TFTs. This work offers deep insights into compensating for the SCEs through the multiscale simulation and experimental verification.