We report on a novel GaAs metal-insulator-semiconductor (MIS) structure exhibiting the interface state densities in the 9.2 x 10(10) eV(-1) cm(-2) with a Si (10 Angstrom)/GaP (12 Angstrom) layer on GaAs. The structure was grown by a combination of molecular beam epitaxy and chemical vapor deposition. The hysteresis and frequency dispersion of the MIS capacitor were lower than 100 mV, some of them as low as 70 mV under a field swing of about +/-1.4 MV/cm. Ex situ solid phase annealing around 500-550 degrees C in N-2 using rapid thermal annealing was high enough to recrystallize the as-deposited Si interlayer at low temperature (similar to 300 degrees C). The 100 kHz frequency response at 77 K suggests that the interface pinning levels are close to the conduction band edge of GaAs. This article reports the first application of a pseudomorphic Si/GaP interlayer to ideal GaAs MIS diodes and exhibits a favorable interface stability with high temperature annealing.