Ultrashallow Ohmic contacts for n-type Ge by Sb δ-doping

We demonstrate ultrashallow Ohmic contacts for n-Ge by the Sb delta-doping and low-temperature Ge homoepitaxy. We find that the segregation effect of Sb on Ge (111) is lower than that on Ge (100) for growth temperatures below 400 degrees C. Consequently, we achieve the delta-doping for Ge (111), having very high concentrations above 10(20) cm(-3) and abrupt profiles within nanometer-scale widths. By introducing the delta-doping to atomically controlled metal/Ge Schottky contacts, completely symmetric current-voltage characteristics, that is, low-resistivity Ohmic contacts are obtained owing to the effective tunneling conduction through the Schottky barrier. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3503587]