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

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 (Y 2 O 3 ) gate dielectric film annealed in high-pressure O 2 . Interface state density in the upper half of the band gap is reduced to 10 11 cm -2 eV -1 and the peak effective mobility is increased up to 1,500 cm 2 V -1 s -1 . This mobility enhancement is attributed to the suppression of GeO desorption or to passivation of the imperfect interface GeO 2 layer by diffused Y 2 O 3 . There is no temperature dependence of the observed mobility, which suggests that intrinsic phonon scattering is still not dominant.