Study of GaSb Layers Grown on Ga/Si(111)-\sqrt{3}\times\sqrt{3} by Scanning Tunneling Microscopy

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GaSb layers grown on a Ga-terminated Si(111) surface have been studied by ultrahigh-vacuum scanning tunneling microscopy. Two types of two-dimensional islands are locally formed on the initial GaSb growth layer on Ga/Si(111)-\sqrt{3}\times\sqrt{3} at a Ga coverage of about 1.2 ML and a Ga/Sb ratio of 4.4. The first type of island is higher than the initial growth layer by a bi-atomic step height. The triangular protrusions on this island correspond to those on the initial GaSb layer. A hexagonal pattern that is higher than the initial growth layer by double the height of the bi-atomic step is observed on the second type of island. Protrusions in the pattern are arrayed at approximately 0.8 nm intervals, which is the distance between twice the unit cell length of Si and GaSb, along the intrinsic direction of the Si(111) surface. Defect lines similar to the misfit dislocation network are observed on the island. These results suggest that the island corresponds to the slightly lattice-relaxed GaSb third layer. A three-dimensional island is formed on the third GaSb layer as GaSb coverage increases. These results indicate that the third GaSb layer is the nucleation site of the three-dimensional GaSb island on Si(111).
2012-08-25