A new switching procedure was applied in the growth of the lattice-matched heterojunction of Ga0.52In0.48P/GaAs by gas source molecular beam epitaxy. The new switching procedure exposed the GaAs surface to the Ga source instead of thermally cracked AsH3 or PH3 before starting the growth of the Ga0.52In0.48P layer. The interface charge density and the conduction band offset were determined by measuring the Schottky barrier height using current versus voltage and capacitance versus voltage characteristics. The interface charge density could be reduced to near zero using the new switching procedure with an exposure time of 64 s. The value of the conduction band offset was 0.2 eV at the interface of zero charge.