Dislocation density reduction through annihilation in lattice-mismatched semiconductors grown by molecular-beam epitaxy

Abstract

Epitaxial InAs/GaAs, GaAs/Ge/Si, GaAs/InP, and InAs/InP heterostructures are grown by molecular-beam epitaxy. Transmission electron microscopy studies reveal that, for these heteroepitaxial systems, the threading dislocation density is inversely proportional to the epilayer thickness. At a given thickness, the threading dislocation density is relatively insensitive to lattice mismatch (3.2%<‖Δa‖/a<7.2%), to differences in thermal expansion coefficients (6.9×10−7<‖Δα‖<3.4×10−6 K−1), to interfacial surface chemistry, and to epilayer morphology. Epitaxial layers incorporating growth interrupts produce lower overall defect densities, yet they maintain defect-reduction profiles similar to those observed in layers without the growth interrupt.