High-quality HfO2/HfSe2 gate stack for low-power steep-switching computing devices

Abstract Herein, we report a high-quality gate stack (native HfO 2 formed on 2D HfSe 2 ) fabricated via plasma oxidation, realizing an atomically sharp interface with a suppressed interface trap density (D it ~ 5×10 10 cm − 2 eV − 1 ). The chemically converted HfO 2 exhibits dielectric constant, κ ~ 23, resulting in low gate leakage current (~ 10 − 3 A/cm 2 ) at EOT ~ 0.5 nm. Density functional calculations indicated that the atomistic mechanism for achieving a high-quality interface is the possibility of O atoms replacing the Se atoms of the interfacial HfSe 2 layer without a substitution energy barrier, allowing layer-by-layer oxidation to proceed. The field-effect-transistor-fabricated HfO 2 /HfSe 2 gate stack demonstrated an almost ideal subthreshold slope (SS) of ~ 61 mV/dec (over four orders of I DS ) at room temperature (300 K), along with a high I on /I off ratio of ~ 10 8 and a small hysteresis of ~ 10 mV. Furthermore, we fabricated HfO 2 /HfSe 2 based impact-ionization FET with a separately controlled channel structure, demonstrating the steep-switching characteristics of SS ~ 3.43 mV/dec at room temperature, overcoming the Boltzmann limit. Our results provide a significant step toward the realization of post-Si semiconducting devices for future energy-efficient data-centric computing electronics.