The Role of Barium In the Heteroepitaxial Growth of Insulator and Semiconductors On Silicon

The epitaxial growth of an insulator, BaF2, and semiconductors of the II-VI and the IV-VI families on Si substrates were carried out. In-situ XPS analyses during the growth of the first monolayers were used to study the surface chemical reactions involved. The results point to a common ingredient in these growths: that the Ba atoms are involved in forming interfacial compounds that would facilitate the heteroepitaxies. In the case of BaF2/Si, a BaSi2 compound has been identified previously. In the case of PbTe and CdTe, the heteroepitaxies on Si are made possible with the BaSi2 buffer. As a result, the impinging semiconductor molecules are broken up, and the metallic elements are ejected from the BaSi2 surface. A new surface chemical, BaTe, is thereby formed. These surface Ba compounds appear to be the dominant factors as the crystal orientations of the BaF2, CdTe, and PbTe layers are independent of those of the Si substrates.