Refractory metal contacts to GaAs show great promise for stability during high temperature processing and for high reliabiltiy. In this paper, we report on a study of sputtered W and W-Si contacts to ion-implanted p-GaAs with both Zn and Mg implantations. This study focused on refractory contacts to shallow implanted contact layers that are suitable for devices such as junction field effect transistors and heterojunction bipolar transistors. The very different energy loss mechanisms of Zn and Mg ions result in different levels of implant damage, which is studied by varying the annealing temperatures and measuring the effects on contact and sheet resistances with the transmission line method. For the fabrication schemes investigated, the specific contact resistivity vs. annealing temperature values with implant doses from 1 x 10(14) to 5 x 10(15) cm(-2) are found to vary from non-ohmic to 10(-7) Omega cm(2). Low resistance contacts to shallow ( < 800 Angstrom) implanted layers are achieved.