Physical properties of Co/n-Ge Schottky contacts

TL;DR

This study investigates how interface states and oxide layers affect the physical properties and barrier characteristics of Co/n-Ge Schottky contacts, using microscopy and spectroscopy techniques.

Contribution

It provides new insights into how different cleaning methods and oxide interlayers influence Fermi level pinning and barrier inhomogeneity in Schottky diodes.

Findings

Native Ge oxide causes strong Fermi level pinning.

Oxide interlayers improve contact homogeneity.

Pure GeO2 oxide may enhance depinning efficiency.

Abstract

To investigate the role of the interface state on the physical properties of Schottky contacts, Co/n-Ge Schottky diodes that have undergone various cleaning methods (HF etching and in-situ thermal cleaning) were studied by Transmission Electron Microscopy (TEM), Deep-level Transient Spectroscopy (DLTS) and by a detailed analysis of the temperature dependence of the diodes characteristics. It is shown that Schottky barrier height characteristics are sensitive to the nature of the interface. The strongest Fermi level pinning and the highest spatial inhomogeneities are observed for intimate metal/semiconductor contacts. The presence of a thin oxide interlayer, even of Ge native oxide, allows the Fermi level to be released towards the conduction band and leads to more homogeneous contacts. Finally our results suggest that a pure GeO2 oxide interlayer should present a better depinning efficiency than the native Ge oxide.