Epitaxial Integration and Defect Structure of Layered SnSe Films on PbSe/III-V Substrates

We synthesize epitaxial films of SnSe, a van der Waals (vdW) layered semiconductor, on III-V substrates via molecular beam epitaxy. While direct deposition of SnSe on GaAs(001) surfaces results in polycrystalline growth, the structural similarity between the distorted rocksalt SnSe and a rocksalt PbSe interlayer facilitates ordered quasi-vdW epitaxy of SnSe with only discrete in-plane rotations arising from the lower film symmetry. Toward manipulating the layering of SnSe for improved mechanical, optoelectronic, and ferroelastic/ferroelectric properties, we show that SnSe/PbSe-on-III-V interfaces are structurally commensurate and chemically compatible enough for the passage of sub-unit-cell surface steps and threading dislocations with partial Burgers vectors into the layered lattice from the 3D template. Such interfaces and extended defects result in novel stacking in SnSe along with the potential to crosslink layers across the vdW gap and yield films of mixed dimensionality. We assess the prospect of thermal expansion mismatch relief via sliding vd\AT interfaces in a 3D/layered/3D-bonded heterostructure using PbSe/SnSe/PbSeon-InAs and find this to be ineffective against cracking as dislocation diffusion, grain boundaries, and crosslinking defects embrittle the heterostructure.