Enhanced channel modulation in Aluminum- and Hydrogen-Doped Zinc-Oxide-Based transistors by complementary Dual-Gate operation

Abstract

This study elucidates the enhanced channel modulation by the dual-gate operation of the ultrathin ZnO-based field-effect transistors (FETs). Bottom-gate atomic-layer-deposited zinc oxide (ZnO) transistors exhibit typical n-type enhancement-mode transfer characteristics. However, when equipped with the top Al2O3 layer, the FETs exhibit conductive transfer characteristics. These electrical property changes are attributed to Al2O3-induced hydrogen and aluminum doping effects, which increase carrier concentration. Although Al2O3-induced doping increased field-effect mobility by a factor of 2, a high off current and degraded transconductance swing were observed in FETs. However, operation in dual-gate mode after the deposition of the top-gate electrode resolved these degradations and led to achieving high-performance ZnO FETs: the off current significantly decreased, and noteworthy, field-effect mobility increased by a factor of 5. Temperature-dependent charge transport analysis revealed that the complementary dual-gate operation efficiently filled the localized trap states in the ZnO films, resulting in band-like transport. Thus, it is deduced that the complementary dual-gate operation enhanced channel modulation in the Al2O3-induced hydrogen- and aluminum-doped ZnO channel, resulting in high-performance ZnO FETs.