Arsenic-induced etched nanovoids on GaSb (100)

Abstract

We describe in situ nanoscale etch-pit formation on GaSb ͑100͒ surfaces as a result of exposure to an As 2 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 ͕111͖ 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 ϳ25 nm wide and 50-80 nm long and 10-70 nm deep, with density of ϳ1 ϫ 10 9 /cm 2 . Subsequent GaAs overgrowth proceeds by a coalescence mechanism leaving interfacial nanovoids and finally highly planar bulk layers.

Growth Mode and Defect Evaluation of GaSb on GaAs Substrate: A Transmission Electron Microscopy Study

“…16 The bright-field plan-view TEM image of 9 ML GaSb grown on GaAs is shown in Figure 4(a). It indicates that the initial IMFs form along both [110] and [1][2][3][4][5][6][7][8][9][10] directions on the surface, and reveals the perfect alignment between two neighboring IMF arrays on opposite sides of the small IMF arrays. As these two IMF arrays continue to grow laterally, the distance separating them decreases accordingly, until the two IMF arrays become contiguous.…”

“…Under the IMF growth mode, the 7.8% lattice mismatch between GaSb epilayer and GaAs substrate is accommodated by 2D IMF arrays along [110] direction as well as [1][2][3][4][5][6][7][8][9][10] direction. When the surface is As-stabilized instead of Ga-rich prior to the deposition of GaSb, the resulting epitaxial layer has a high density of threading dislocations.…”

“…The density of TDs, roughly estimated from TEM images, is ∼10 9 cm −2 . [1][2][3][4][5][6][7][8][9][10][11] direction. 16 The bright-field plan-view TEM image of 9 ML GaSb grown on GaAs is shown in Figure 4(a).…”

“…[3][4][5][6] The heterostructures of Sb-based compound semiconductors grown on GaAs substrates can exhibit a type-II (staggered) bandgap lineup featuring recombination from spatially indirect excitons. * Author to whom correspondence should be addressed.…”

Electron tomography on nanopores embedded in epitaxial GaSb thin films

“…Finally, the aspect of surface reconstruction and the incorporation of adatoms have to be considered which severely depends on the formation conditions. Huang et al (2007), for instance, have observed an amorphous covering which they attribute to excess Sb or residual AsSb reaction products.…”