Arsenic-induced etched nanovoids on GaSb (100)

We describe in situ nanoscale etch-pit formation on GaSb (100) surfaces as a result of exposure to an As2 flux in molecular beam epitaxy. The pits form as a result of an Sb-displacement reaction that occurs between the GaSb substrate and the impinging As adatoms. The nanoscale surface features are highly crystallographic with a strong preference for {111} planes, similar to other etching techniques. Nanopit dimensions and density increase with As exposure time. For the 60 s exposure analyzed in this article, the pits vary in both size and shape with average dimensions ∼25 nm wide and 50–80 nm long and 10–70 nm deep, with density of ∼1×109/cm2. Subsequent GaAs overgrowth proceeds by a coalescence mechanism leaving interfacial nanovoids and finally highly planar bulk layers.