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A low resistance Zn/Pd ohmic contact scheme to p-InP based on the solid phase regrowth principle has been investigated. The lowest contact resistivity (mid 10/sup -5/ /spl Omega/-cm/sup 2/) has been obtained for contacts with an atomic ratio of Zn to Pd of /spl sim/1.5. The solid phase regrowth process has been confirmed in the Zn/Pd/InP system. In addition to the solid phase regrowth process, a Zn/sub 3/P/sub 2//InP heterojunction is formed at the contact/semiconductor interface. The ohmic contact formation mechanism is rationalized with the formation of Zn/sub 3/P/sub 2//InP heterojunction. Also, it was found that the TLM plot for the thick-Zn (>600 /spl Aring/) sample started to show abnormal data distribution for annealing temperatures higher than 480/spl deg/C. This abnormal behavior may be caused by the lateral Zn diffusion from the excess Zn in the contact pads into the off-mesa area during annealing.