MOCVD Growth and Characterization of GaP on Si

GaP and GaP/GaAsP epitaxial layers have been grown on Si substrates by metalorganic chemical vapor deposition (MOCVD), and characterized by SEM and TEM plan-view and cross-sectional examination. At growth temperatures ranging from 600 to 800°C, the initial stages of growth were dominated by three-dimensional nucleation. TEM studies showed that the nuclei were generally misoriented with respect to each other, yielding, upon coalescence, polycrystalline layers. The growth of single-crystal layers could be achieved only by nucleating a 30-50 nm layer of GaP at 500°C, followed by continued growth at 750°C. A high density of structural defects (∼10¹¹ cm^-2) was observed at the Si/GaP interface, decreasing to ∼10⁸ cm^-2, 2 μ away from the interface. The use of 2° off (100) Si substrates resulted in GaP layers free of antiphase domains. These results and their implications are discussed.