Electrical Behavior of Germanium Oxide/Germanium Interface Prepared by Electron-Cyclotron-Resonance Plasma Oxidation in Capacitance and Conductance Measurements

In this letter, we describe the electrical behavior of the GeO_x and p-type Ge interface on the basis of capacitance and conductance measurements. The primary conclusion of this work is that when the Ge surface is biased in the depletion region, the frequency response of interface traps in the lower half of the Ge band-gap is so fast that there is no significant frequency dispersion observed in the capacitance measurements over a typical frequency range of ≤ 1 MHz. As a result, the density and energy distributions of the interface traps cannot be determined by a conventional method of combined high-frequency and low-frequency capacitance measurements. Instead, a comparison of the measured capacitance with a theoretical capacitance calculated for a system with no interface traps must be conducted to obtain information on the interface traps. Furthermore, the conductance method provides information on the interface traps in the upper half of the p-type Ge band-gap.