High-Electron-Mobility Ge n-Channel Metal–Oxide–Semiconductor Field-Effect Transistors with High-Pressure Oxidized Y₂O₃

Abstract

This letter presents a significant improvement of electron mobility in a germanium (Ge) n-channel metal–oxide–semiconductor field-effect transistor with a yttrium oxide (Y2O3) gate dielectric film annealed in high-pressure O2. Interface state density in the upper half of the band gap is reduced to 1011 cm-2 eV-1 and the peak effective mobility is increased up to 1,500 cm2 V-1 s-1. This mobility enhancement is attributed to the suppression of GeO desorption or to passivation of the imperfect interface GeO2 layer by diffused Y2O3. There is no temperature dependence of the observed mobility, which suggests that intrinsic phonon scattering is still not dominant.