Versatile strain relief pathways in epitaxial films of (001)-oriented PbSe on III-V substrates

Abstract

PbSe and related IV-VI rocksalt-structure semiconductors have important electronic properties that may be controlled by epitaxial strain and interfaces, thus harnessed in an emerging class of IV-VI/III-V heterostructures. The synthesis of such heterostructures and understanding mechanisms for strain-relief is central to achieving this goal. We show that a range of interfacial defects mediate lattice mismatch in (001)-oriented epitaxial thin films of PbSe with III-V templates of GaAs, InAs, and GaSb. While the primary slip system {100}<110> for dislocation glide in PbSe is well-studied for its facile glide properties, it is inactive in (001)-oriented films used in our work. Yet, we obtain nearly relaxed PbSe films in the three heteroepitaxial systems studied with interfaces ranging from incoherent without localized misfit dislocations on 8.3% mismatched GaAs, a mixture of semi-coherent and incoherent patches on 1.5% mismatched InAs, to nearly coherent on 0.8% mismatched GaSb. The semi-coherent portions of the interfaces to InAs form by 60{\deg} misfit dislocations gliding on higher order {111}<110> slip systems. On the more closely lattice-matched GaSb, arrays of 90{\deg} (edge) misfit dislocations form via a climb process. The diversity of strain-relaxation mechanisms accessible to PbSe makes it a rich system for heteroepitaxial integration with III-V substrates.