Conduction Band offset in GeO_2/Ge Stack Determined by Internal Photoemission Spectroscopy

摘要

The conduction band offset (CBO) at GeO_2/Ge interface has been systematically investigated by using internal photoemission spectroscopy (IPE). Irrespective of the metal gate electrode (Au or Al) and Ge substrate type (p- or n- type) variance, the energy barrier for the electrons of Ge valence band into GeO_2 conduction band is determined to be 2.34 ± 0.1eV, thus yielding the CBO of 1.65 ± 0.1eV. Such as-obtained >1.5eV CBO agrees well with previous IPE results measured on the ultra-thin GeO_x/High-k oxide stacks and theoretical calculation without the valence alternation pair, and gives further support of GeO_2 as potential passivation layer for the future Ge-based CMOS devices.