DISLOCATIONS IN CdTe HETEROEPITAXIAL STRUCTURES ON GaAs(301) AND Si(301) SUBSTRATES
Initial stages of ZnTe growth on GaAs(301) and Si(301) substrates by the method of molecular beam epitaxy are investigated by means of in situ one-wave ellipsometry. Layer-by-layer growth of the ZnTe film is observed on GaAs(301) substrates, whereas 3 D nucleation occurs during epitaxy on Si(301) substrates. Misfit dislocations (MDs) are inserted into the ZnTe film during the growth of the first monolayers. Owing to MDs, the film lattice turns with respect to the substrate lattice, which is confirmed by X-ray measurements. Threading segments of MDs in CdTe/ZnTe/GaAs(301) and CdTe/ZnTe/Si(301) heterostructures are subjected to etching. The etch dislocation pits are found to have different shapes, which testifies to different types of threading dislocations. In the case of layer-by-layer etching, the dislocation density is found to increase inward the CdTe film, which testifies to annihilation of dislocations in the course of growth of CdTe films. The dislocation annihilation rate is higher in films grown on GaAs(301) than in those grown on Si(301). A possible reason is the higher mobility of dislocations in CdTe films on GaAs(301) substrates.