This paper presents a current transport mechanism of Pd metal-semiconductor-metal (MSM) GaAs diodes with a Schottky contact material formed by intentionally mixing SiO2 into a Pd metal. The Schottky emission process, where the thermionic emission both over the metal-semiconductor barrier and over the insulator-semiconductor barrier is considered on the carrier transport of a mixed contact of Pd and SiO2 (MMO) MSM diodes, is analyzed. The image-force lowering is accounted for. In addition, with the applied voltage increased, the carrier recombination is thus considered. The simulation data are presented to explain the experimental results clearly.