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 are controlled by epitaxial strain and interfaces and can be harnessed in the emerging class of IV-VI/III-V hybrid heterostructures. The synthesis of such heterostructures and understanding mechanisms for strain relief in these materials is central to achieving this goal. We show that a range of interfacial defects mediate lattice mismatch in $(001)\ensuremath{-}\mathrm{oriented}$ epitaxial thin films of PbSe and III-V templates of GaAs, InAs, and GaSb. While the primary slip system ${100}<110>$ in PbSe is well studied for its facile dislocation glide even at low temperatures, it is inactive in $(001)\ensuremath{-}\mathrm{oriented}$ films 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 semicoherent and incoherent patches on 1.5% mismatched InAs, to nearly coherent on 0.8% mismatched GaSb. The semicoherent portions of the interfaces to InAs form by 60\ifmmode^\circ\else\textdegree\fi{} misfit dislocations gliding on higher-order ${111}<110>$ slip systems. On the more closely lattice-matched GaSb, arrays of 90\ifmmode^\circ\else\textdegree\fi{} (edge) misfit dislocations form via a climb process. This diversity of strain-relaxation mechanisms accessible to PbSe makes it a convenient material for epitaxial integration in hybrid heterostructures.