Pd/Zn/Au contacts to p-In0.53Ga0.47As/InP with various types of barrier layers to the indiffusion of Au have been examined by Rutherford backscattering spectrometry (RES). For the metallizations with a barrier layer of Pd, the aging of the contacts at 400 degrees C for 20 h produced a widespread indiffusion of Au for all thicknesses of the Pd. In comparison, the incorporation of a layer of Pt or amorphous LaB6 in the contacts prevented an indiffusion of Au and significantly reduced any outdiffusion of the semiconductor elements. The presence of the barrier layer of Pt or LaB6 produced little or no detrimental increase in rho(c), for this contact system. In the as-deposited Pd-based contacts, a layer of Zn in the structure was necessary in order to produce a minimum value of rho(c). After annealing at 500 degrees C, a specific contact resistance in the range 8-10x10(-6) Omega cm(2) was obtained for all of the contacts based on Pd/Zn/Au. A comparison has been made with the characteristics of Pt/Ti/Pt/Au contacts to p-In0.53Ga0.47As/InP which were shown as stable against the indiffusion of Au.