Highly ordered embedded nanostructures of rare-earth monopnictides can be formed within III-V semiconductor heterostructures providing a new degree of control over the structural and transport properties of the heterostructures. Materials such as ErAs and ErSb are thermodynamically stable with GaAs and GaSb respectively, and in both cases a common group-V sublattice is maintained throughout the heterostructures. In both the arsenides and antimonides, co-deposition at concentrations above a few atomic percent results in the formation of nanoparticles and nanorods. The shape of the nanostructures is strongly dependent of the growth surface including reconstructions, stoichiometry, temperature, and crystallographic orientation. Codeposition of Er with GaAs can produce nanoparticles or ordered nanorods oriented along either the [111] or [211] directions depending on aforementioned conditions[1]. While codeposition of Er with GaSb produces either particles or nanorods oriented primarily along the [100] direction. STM of the GaAs(311)A and B surfaces during the initial stages of nucleation show that following the deposition of a fractional monolayer of ErAs, embedded growth of ErAs particles are observed on the B surface, while the A surface shows primarily surface cluster formation. MBE growth of GaAs on (311)A and B orientations produces relatively flat surfaces with uniquely different (8×1) reconstructions. Codeposition of Er with GaAs results in significant roughening of the surface during growth due to anisotropic diffusion of Ga and Er along the <233> and <011> directions and the general tendency of GaAs not to wet ErAs(100) surfaces. The [211] orientation of the ErAs nanorods on the surface is found to result from preferential growth along the (1 -1 -1) plane on Ga-polar A surfaces. While the angle between the (1 -1 -1) and surface normal remains less than or equal to 90º, the [211] orientated growth is supported. The {111} surface of the rocksalt ErAs is typically a high-energy surface; however, the Ga-rich (1 -1 -1) plane provides a flux mediated epitaxial growth surface for the ErAs analogous to a vapor-liquid-solid type of growth. In-situ RHEED, LEED and STM surface studies will be presented along with a detailed growth model to explain differences in the growth process and in nanorod formation for different substrates and substrate orientations.

Supported by AFOSR FA9550-10-1-0119 and ARO W911NF-07-1-0547. [1] T.E. Buehl, C.J. Palmstrøm, and A.C. Gossard, J. Vac. Sci. Technol. B 29, 03C108-1, 2011.