Interactions between Sb and As on InAs(0 0 1) surfaces

Interfacial broadening that occurs due to intermixing of Sb and As at the interfaces is a challenge for growing high quality mixed anion heterostructures. In this work, we examine the atomic scale interaction between As and Sb. Experimental observations show that the surface consists primarily of (4 × 3) and c(4 × 4) reconstructions as a function of As and Sb overpressure. Density functional theory calculations confirm the experimental phase diagram and show that many of the reconstructions contain both Sb dimers and sub-surface Sb. This indicates concurrent mechanisms for interfacial broadening: some Sb atoms are weakly bound in dimer sites and segregate during growth, while some Sb atoms are driven to infiltrate the crystal and intermix with As. The calculations also predict a stoichiometric Sb-terminated α2(2 × 4) to be stable, suggesting that abrupt III-As/III-Sb heterostructures could be obtained by growing on this surface. While not trivial to achieve, this surface can be experimentally obtained by depositing Sb directly on an In-terminated surface.