The contact properties of alloyed Ni/Au-Ge/Mo/Au metallization to npoststagger+In0.5Ga0.5P epilayers grown by gas-source molecular beam epitaxy on GaAs substrates are reported. A minimum specific contact resistance of 10−5 Ωcm2 was obtained forn = 2 × 1019 cm−3 material after alloying at 360° C for 20 sec. Above this temperature outdiffusion of lattice elements and reactions of the metallization with the In0.5Ga0.5P lead to severe morphological changes and degraded contact properties. From the temperature dependence of the contact resistance, thermionic emission was identified as the predominant current transport mechanism in these contacts.