We investigate PdGe and NiGe based ohmic contacts to n-GaAs by comparison between the PdGeTiAu contact and NiGeTiAu ohmic contact under same experimental condition. The minimum contact resistance of PbGeTiAu contact is considerably lower than that of NiGeTiAu contact. In addition, PdGeTiAu contact has much wide processing windows for annealing temperature as well as annealing time. X-ray diffraction results show that formation temperature of germanide(PbGe and NiGe) strongly influences electrical properties of the contacts.