The microstructural and electrical properties of Er-germanides formed by a solid state reaction between Er and Ge have been investigated at different germanide formation temperatures from 400 to 700 degrees C. Er(26)Ge(23) and Er(3)Ge(4) phases were formed at a germanidation temperature of 400 degrees C, followed by the formation of Er(3)Ge(4) and Er(2)Ge(3) at 500 to 600 degrees C and then ErGe(2.16) at 700 degrees C. The sheet resistance gradually decreased with increasing annealing temperature up to 600 degrees C, which could be associated with the phase transformation from Er-rich to Ge-rich Er-germanides. Er-germanides on n-type Ge showed Schottky behavior at low formation temperatures of less than 600 degrees C. Above 600 degrees C they exhibit Ohmic behavior. However, due to strong Fermi level pinning, Er-germanide contact to p-type Ge substrates was demonstrated to be Ohmic regardless of the annealing temperatures. The conversion of Schottky to Ohmic behavior could be attributed to a significant increase in current in the forward and reverse biases caused by the formation of square-shaped microvoids driven by Ge out-diffusion near the interface between germanides and the Ge substrate. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3594746] All rights reserved.