Interface Structures and Electrical Properties of Micro-Fabricated Epitaxial Hf-Digermanide/n-Ge(001) Contacts

Abstract

We investigated the interface crystalline structure and electrical conduction properties of epitaxial Hfdigermanide(HfGe2)/n-Ge(001) contacts with different electrode sizes of 20, 45, and 90 μm prepared via microfabrication. It was found that the microfabrication process improved the interface uniformity of the HfGe2/n-Ge(001) contacts. Detailed transmission electron microscopy analysis confirmed the growth of epitaxial HfGe2 on Ge(001) and implied that microfabrication suppressed the strain relaxation of HfGe2. These results imply that the applied strain of the epitaxial HfGe2, which was controlled via microfabrication in this study, is a possible parameter that may be used to improve the interface uniformity HfGe2/n-Ge(001) contacts. The Schottky barrier heights (SBHs) of the HfGe2/n-Ge(001) contacts estimated from the capacitance-voltage characteristics were small and in the range of 0.4 to 0.5 eV independent of the electrode size. Furthermore, considering the temperature dependence of the current density-voltage characteristics, we found that both the thermionic field emission current and the tunneling current through the interface dipole layer were possibly flowed in series and that the SBH for the 20 μm sample was 0.24 eV, whereas that for both the 45 and 90 μm samples were 0.31 eV.