The film/substrate orientation relationships of CdTe grown on Si and GaAs by low pressure metalorganic chemical vapour deposition

Abstract

CdTe epitaxial layers have been grown on (100) Si, (100) GaAs and (111) GaAs substrates by low pressure metalorganic chemical vapour deposition method with dimethylcadmium (DMCd) and diethyltelluride (DETe) as source materials. The orientation relationships between epitaxial layers and substrates are determined experimentally by X-ray diffraction, and the results show that (100) and (111) oriented CdTe epitaxial layers with parallel epitaxial relationships can be grown on (100) and (111) GaAs substrates, respectively. However, the epitaxial orientation relationship is (111)CdTe ‖ (100) Si for the Si substrate. To investigate the factors which determine the orientation relationships, plane-view transmission electron microscopy observations of the interface were carried out. The results seemed to indicate the existence of a thin amorphous layer between CdTe epitaxial layer and Si substrate, and a dislocation structure in the CdTe/GaAs interface. On the basis of these observations, a Te-O bond atomic arrangement of the CdTe/Si interface is tentatively suggested and discussed for the (111) CdTe epitaxial layer formed on (100) Si substrate. On the other hand, the dislocation interface probably acts as a stress buffer layer and plays a major role for the parallel growth orientation in the (100) CdTe ‖ (100) GaAs case.