[摘要]：Typical contacts to n-Ge result in high specific contact resistivity (rho(C)) or rectifying behaviour due to Fermi level pinning (resulting in high barrier heights) and low dopant activation generally observed for n-Ge. In this work, we fabricated and studied ohmic contacts to n-type Ge prepared by Ni germanidation of samples with As ion implantation for two different approaches: (1) dopant activation by sub-melt laser anneal (LA) prior to germanidation and (2) Snowplow, i.e., dopant segregation during Ni germanidation without previous thermal activation. Low resistivity ohmic contacts of 8 x 10(-7) Omega cm(2) for LA and 2 x 10(-5) Omega cm(2) for Snowplow were obtained using circular transfer length method to determine rho(C). We show contacts to be thermally stable to 350 degrees C. Furthermore, by studying the temperature dependence of rho(C), we clarify that the underlying cause of the low contact resistivity for both approaches is the high active dopant concentration obtained. We find the results in both cases to be consistent with the thermionic field-emission mechanism for a barrier height of 0.75 eV and with active dopant concentrations of 3 x 10(19) cm(-3) for LA and 1.5 x 10(19) cm(-3) for Snowplow samples. (C) 2011 American Institute of Physics. [doi:10.1063/1.3666045]
