Ryuto Machida

Study of Initial Growth Layer of GaSb on Si(111) by Scanning Tunneling Microscopy

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.

Growth of GaSb dots nucleation layer and thin-film GaSb on Si(100) substrate by molecular beam epitaxy

Gallium antimonide (GaSb) dots and thin-film GaSb using GaSb dots as nucleation layer were grown on a 2-inch Si(100) substrate by molecular beam epitaxy (MBE). Compared to our previous works in ultrahigh vacuum scanning tunneling microscopy (UHV-STM) system, higher-density and smaller-size GaSb dots were formed on the Si(100) substrate at 300°C. It is considered that the difference of Sb species and growth rate affects the diffusion length of Ga atoms, and that caused the density and size of GaSb dots higher and smaller in case of the MBE growth. Furthermore, the domain structure of GaSb with step and terrace surface structures was formed when a 100-nm-thick GaSb was also grown using the GaSb dots nucleation layer on the Si(100) substrate at 500°C, indicating that GaSb dots are quite useful as nucleation layer for epitaxial growth of thin-film GaSb on the large-area Si(100) substrate.

Effect of Types of Ga/Si(111) Reconstructed Structure on Growth Morphology of GaSb Island

Ryuto Machida*, Ryusuke Toda, Keisuke Yoshiki, Shinsuke Hara, Katsumi Irokawa, Hirofumi Miki, Akira Kawazu, and Hiroki I. Fujishiro Faculty of Industrial Science and Technology, Tokyo University of Science, Noda, Chiba 278-8510, Japan Faculty of Science and Technology, Tokyo University of Science, Noda, Chiba 278-8510, Japan Faculty of Science and Engineering, Tokyo Denki University, Hatoyama, Saitama 350-0394, Japan

Study of GaSb Layers Grown on Ga/Si(111)-√3×√3 by Scanning Tunneling Microscopy

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)-√3×√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).