Growth conditions have investigated for growing high quality In 0.3Ga0.7As and In0.5Ga0.5As on GaAs substrate by metalorganic chemical vapor deposition method. Annihilation reactions between threading dislocations observed by transmission electron microscopy are experimental evidences to confirm threading dislocations had been blocked in InxGa1-xAs buffer layers. A high quality smooth surface In0.5Ga0.5As epi-film with threading dislocation density of 2×106 cm-2 was achieved at growth temperature of 490 oC. Metal-oxide-semiconductor capacitor devices fabricated on In0.5Ga0.5As/GaAs perform nice capacitance-voltage response, with small frequency dispersion. The conductance contours indicate that the Fermi level moves freely to the lower part of the InGaAs bandgap without pinning.