Nucleation control and interface structure of rocksalt PbSe on (001) zincblende III-V surfaces

Abstract

We study the early stages of growth of the IV-VI semiconductor PbSe on (001)-oriented III-V substrates with different surface chemistry and lattice parameter, with the aim of achieving high quality cube-on-cube rocksalt on zincblende epitaxy. We find that PbSe nucleation on bare GaSb, InAs, and GaAs substrates is varied, yet consistently results in mixed orientation growth due to chemistry-dependent interfacial-energy penalties, irrespective of lattice mismatch. To overcome this, we locate a growth window for cube-on-cube single-orientation nucleation of PbSe on III-arsenide surfaces utilizing a high-temperature surface treatment with PbSe flux that we find creates a better template for subsequent low-temperature growth and leads to sharp interfaces. We probe this interface between PbSe and InAs, finding a Chain[Pb,As] atomic arrangement, tantamount to a discontinuous anion sublattice between III-V and IV-VI materials. We also observe a vertical displacement of the first few monolayers of the Se sublattice that we believe has origins in the heterovalency of this interface. Our results point towards surface chemistry as the primary factor governing film orientation, and lattice mismatch governing island coalescence behavior in these heterovalent interfaces with dissimilar crystal structures.