Sb dissociative surface coverage model for incorporation of antimony in GaAsSb layers grown on GaAs (0 0 1) substrates

Sb‐Mediated Tuning of Growth‐ and Exciton Dynamics in Entirely Catalyst‐Free GaAsSb Nanowires

“…As argued before, on highly Sb‐enriched surfaces (anti‐surfactant regime), the incorporation of Sb competes strongly with the detrimental Sb‐As exchange reaction. [ 33–35 ] This exchange reaction is, in fact, highly dependent on growth rate, as observed in literature on planar GaAsSb thin films [ 33,35 ] —that is, when growth rate is slow, the exchange of Sb and As adatoms has much more time to proceed, consequently lowering Sb incorporation, as opposed to high growth rates. We observe exactly this behavior in our NW, which corroborates the existence of an Sb‐rich surface layer limiting the growth and compositional uniformity under excess Sb supply.…”

“…It is well known that due to its small surface energy and large atomic radius, Sb tends to float on the growth surface, forming a dissociative Sb surface segregation layer. [33,34] In dynamic equilibrium, this Sb-rich surface layer promotes an As exchange reaction in existing Ga-Sb bonds and thereby inhibits incorporation of Sb atoms, especially for high critical Sb surface coverages. [34,35] The presence versus absence of such critical Sb segregation layer has intriguing consequences for many aspects in growth, as well as structural and compositional properties as we show below.…”

“…In contrast, for larger Sb supply a transition to a Sb-rich surface reconstruction with significant Sb surface coverage can be anticipated, based on observations in planar layers. [34,35,37] Under such Sb-enriched surface, both As and Ga adatoms rapidly exchange their overlayer site for a sub-surface site, which strongly inhibits their adatom diffusion, [38] limiting axial growth. Below, we illustrate the effects of Sb-mediated adatom diffusion behavior in a more comprehensive way.…”

“…We suggest that the surface energetics must be clearly modified, for example, by alterations in the usual As-rich surface reconstruction via different Sb surface atomic densities, which influence surface diffusion. [33][34][35]37,38] Further experiments, such as desorption mass spectrometry highlighting sub-critical Sb surface coverages, as well as analysis of Sb-mediated surface structure via scanning tunneling microscopy and X-ray photoemission studies, along with atomistic modelling will be necessary for fully complete understanding.…”

Sb-saturated high-temperature growth of extended, self-catalyzed GaAsSb nanowires on silicon with high quality

“…In fact, this is expected based on the well-known growth rate dependencies of Sb-incorporation in GaAsSb layers. Zhang et al [35] modelled the composition of VS-grown GaAsSb layers on GaAs and found that at higher growth rate, the Sb-content is increased because the As-for-Sb exchange reaction, which occurs on the surface of the layer, has less time to proceed until the next layer is grown. In our case, a higher Ga-rate increases the VS growth rate on the sidewalls, which, in agreement with these effects, increases the Sb-content.…”