The growth process and morphology of three‐dimensional GaSb islands grown on a Ga/Si(111)‐√3 × √3 reconstructed surface have been studied by ultrahigh‐vacuum scanning tunneling microscopy and non‐contact atomic force microscopy. Faceted GaSb islands with a density of 1011 cm−2 are formed on Ga/Si(111) in multilayer growth at 350 °C. Hexagonal‐ and pyramid‐shaped islands are formed at 400 °C. Dome‐shaped islands, which are similar to the islands grown on clean Si(111), are only formed at 450 °C. The growth morphology of GaSb islands varies depending on the atomic species terminated on Si(111) and the growth temperature. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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The effect of a low‐temperature‐grown gallium antimonide (LT‐GaSb) layer on the formation of high‐density GaSb islands on a Si(100) substrate was studied using ultrahigh‐vacuum scanning tunneling microscopy (UHV‐STM) and atomic force microscopy. By using an LT‐GaSb layer in the initial growth stage (new growth method), high‐density and small GaSb islands were formed at 500 °C regardless of the type of the reconstructed surface. The density and size of the GaSb islands with the LT‐GaSb layer were estimated to be ∼1.0 × 1011 cm−2 and ∼20 nm, respectively. The STM results showed that the LT‐GaSb layer was composed of an Sb‐rich amorphous GaSb layer. With a rapid increase in temperature under the Sb flux, the LT‐GaSb layer immediately changed into GaSb nuclei with a high density (2.1 × 1011 cm−2) and small size (11 nm). It is suggested that these high‐density and small GaSb islands grow from the GaSb nuclei, which act as crystal seeds.

The initial growth layer of GaSb on a Si(111) surface has been studied by scanning tunneling microscopy. After the simultaneous deposition of Ga and Sb atoms at 0.85 and 1.45 monolayers, respectively, Sb/Si(111)-2×1 and -√3×√3-R30° structures were formed on a large area of the Si(111) surface. In addition, the protrusions of the cross-hatch pattern, which was higher than that of the Sb/Si(111) structures by a bilayer height, were observed. The pattern area is suggested to correspond to the initial growth layer of GaSb. Three types of layer domains were observed. These domains are formed because of the strain caused by the lattice mismatch between GaSb and Si. Based on both cases of group-III and -V polar surface structures, the atomic structural models of these domains are proposed: one domain is a layer with strain relaxation, formed by the reconstruction of on-top atoms; the second is a layer formed on the reconstructed Si surface; and the third is a layer with uniaxial strain relaxation. Three-dimensional hut-shaped islands were observed to form infrequently on the local surface area. A cross-hatch pattern similar to the initial growth layer was observed on the facets of these islands. It is suggested that the islands are composed of GaSb crystals. An initial growth layer of GaSb was observed around some of the islands. From these results, we speculate that the GaSb dot crystals grow epitaxially on the initial layer.