Surface Orbitals and Facet Tolerance in III-V Quantum Dots.

Recent synthesis methods have extended the range of III-V semiconductors available as colloidal quantum dots (QDs) from In-based to Ga-based compounds. As a result, the same band-edge transition can be attained through different combinations of QD size and composition, such that QDs can be optimized for specific applications. Here, we direct this selection problem by a computational screening of surface orbital formation in III-V QDs. Using a multitude of QD models, we demonstrate that tolerance for surface orbitals related to unpassivated anion facets increases according to P < As < Sb and Al < In < Ga, with GaSb models often showing no such orbitals. We relate these trends to the lower energy of the anion dangling bond relative to that of the valence-band edge. The same approach predicts that In-based QDs will be most tolerant and GaAs and GaSb modestly tolerant for surface orbitals related to unpassivated cation facets. Combining both results, we conclude that GaSb, GaAs, and InSb offer the best compromise of anion and cation facet tolerance, an essential insight to select the best III-V QD for a given application.