High‐κ Dielectric (HfO2)/2D Semiconductor (HfSe2) Gate Stack for Low‐Power Steep‐Switching Computing Devices

Abstract

AbstractHerein, a high‐quality gate stack (native HfO2 formed on 2D HfSe2) fabricated via plasma oxidation is reported, realizing an atomically sharp interface with a suppressed interface trap density (Dit ≈ 5 × 1010 cm−2 eV−1). The chemically converted HfO2 exhibits dielectric constant, κ ≈ 23, resulting in low gate leakage current (≈10−3 A cm−2) at equivalent oxide thickness ≈0.5 nm. Density functional calculations indicate that the atomistic mechanism for achieving a high‐quality interface is the possibility of O atoms replacing the Se atoms of the interfacial HfSe2 layer without a substitution energy barrier, allowing layer‐by‐layer oxidation to proceed. The field‐effect‐transistor‐fabricated HfO2/HfSe2 gate stack demonstrates an almost ideal subthreshold slope (SS) of ≈61 mV dec−1 (over four orders of IDS) at room temperature (300 K), along with a high Ion/Ioff ratio of ≈108 and a small hysteresis of ≈10 mV. Furthermore, by utilizing a device architecture with separately controlled HfO2/HfSe2 gate stack and channel structures, an impact ionization field‐effect transistor is fabricated that exhibits n‐type steep‐switching characteristics with a SS value of 3.43 mV dec−1 at room temperature, overcoming the Boltzmann limit. These results provide a significant step toward the realization of post‐Si semiconducting devices for future energy‐efficient data‐centric computing electronics.