HETEROEPITAXIAL GROWTH OF (CA,SR)F2 ON SI(100) SUBSTRATES BY MOLECULAR-BEAM EPITAXY

Heteroepitaxial growth of (Ca,Sr)F2, which is lattice-matched with GaAs, on Si(100)4° off toward [011] substrate has been investigated for GaAs/insulator/Si structures. The (Ca,Sr)F2 layer grown directly on Si(100)4° off substrate by molecular beam epitaxy (MBE) has a columnar structure. A single crystal of the (Ca,Sr)F2 layer, however, could be grown on CaF2/Si(100)4° off structure. The optimum growth temperatures of the top (Ca,Sr)F2 layer for obtaining good crystallinity in the (Ca,Sr)F2/CaF2/ Si(100)4° off structures were in the range of 400-500°C. The (Ca,Sr)F2 layers grown at higher temperatures than this were cracked along cleavage planes by thermal stress. Very fine faceted morphologies were observed on the surfaces. The top angles of the facets in the (011) cross-sections were changed from sharp to dull with increasing growth temperatures. This suggests that the stability of the crystal planes in the mixed fluoride depends on temperature. © 1990.