The electrical and microstructural properties of the PdSi based ohmic contacts on n-InP are discussed in the research. A low specific contact resistance of 2.25 x 10(6) Omega cm(2) is obtained on Au/Si/Pd/n-InP contact after rapid thermal annealing (RTA) at 450 degrees C for 30 s. The low contact resistance can be maintained at the order of 10(6) Omega cm(2) even up to 500 degrees C annealing. From the Auger analysis, it is found that both the outdiffusion of In and the indiffusion of Si into the InP surface occurred at the ohmic contact sample. The formation of the Pd3Si compound lowered the barrier of the contact. The reactions between Pd and InP of the contact, forming In vacancies, and leading the doping of Si to the InP contact interface. (C) 2009 Elsevier B. V. All rights reserved.