We report on the investigation of a low resistance Pd/Zn/Pd contact top-InGaAsP (&lgr;=1.14 &mgr;m). The contact had a minimum contact resistivity of ∼3×10−7&OHgr; cm2to the substrate doped to 2×1018cm−3. The samples showed rather uniform surface and interfacial morphologies. X-ray studies showed the formation of a PdZn phase for samples annealed below 400 °C and this phase started to decompose at temperatures higher than 400 °C. Pd-III compounds (Pd2Ga5and PdIn3) also started to form for annealing temperatures higher than 400 °C. The ohmic behavior can be understood in terms of the decomposition of the PdZn phase and the formation of Pd-III compounds for samples annealed at 400 °C or higher. The thermal stability of this contact at 400 °C was found to be stable, which is important for device applications. ©1997 American Institute of Physics.