Influence of Microdefects on the Generation of Dislocations in Homoepitaxial Gallium Phosphide Layers Grown on LEC Substrates

GaP LEC substrates doped with sulphur (N_D – N_A roughly (3–7) × 10¹⁷ cm⁻³) were characterized by transmission electron microscopy. This material was found to contain microdefects such as perfect perismatic dislocation loops, and spherical precipitates. Cross-sectional TEM investigations perfomed have shown that above all perfect dislocation loops lying directly at the substrate/layer interface are sources for the formation of extended dislocations propagating through the epitaxial layer. Using the methods of selective photoetching and AB-etching on (110) cleavage faces this phenomenon was observed, too.