AVS 50th International Symposium
    Semiconductors Friday Sessions
       Session SC+NS-FrM

Paper SC+NS-FrM6
Ge Island Nucleation on Large-Miscut Si(001) Surfaces

Friday, November 7, 2003, 10:00 am, Room 321/322

Session: Low Dimensional Structures and Amorphous Silicon
Presenter: K. Ohmori, University of Illinois at Urbana-Champaign
Authors: K. Ohmori, University of Illinois at Urbana-Champaign
Y.L. Foo, University of Illinois at Urbana-Champaign
S. Hong, University of Illinois at Urbana-Champaign
J.G. Wen, University of Illinois at Urbana-Champaign
J.E. Greene, University of Illinois at Urbana-Champaign
I. Petrov, University of Illinois at Urbana-Champaign
Correspondent: Click to Email
We study self-organized growth of Ge nanostructures on Si surfaces with large off-[001]-axis miscut as a function of the tilt angle @theta@ and in-plane azimuth angle @phi@ with respect to the [100] direction. The off-axis surfaces were fabricated using focused ion beam (FIB) to precisely pattern a variety of structures such as trenches, concave cones, and square-pyramids on Si(001) surfaces. During the FIB processing, the Si(001) substrates were covered with 200-nm-thick protective SiO@sub 2@ films. A 50-nm-thick Si buffer layer was grown at 800°C by ultrahigh vacuum gas-source molecular beam epitaxy using Si@sub 2@H@sub 6@ precursor prior to Ge deposition at 600°C using Ge@sub 2@H@sub 6@. The nominal thickness of the Ge layer is about 7 ML. Diverse Stranski-Krastanov growth modes (Ge domes, elongated islands, and nanowires) were observed as a function of @theta@ and @phi@, which we attribute to differences in anisotropic-strain relief mechanism. While on a vicinal (001) surface (@theta@ = 0.3°), dome-shaped Ge islands with a density of 30.9 µm@super -2@ are formed, the island density increases by 30% on a surface with @theta@ = 5° for all @phi@-values . In the range of @theta@ = 10 to 20°, elongated island shapes emerge in directions near @phi@ = 45 n° (n = 1, 3, 5, 7), while at @phi@ = 90 n° (n = 0, 1, 2, 3) island nucleation is suppressed. With @theta@ @>=@ 25°, Ge nanowires with a length of about 2 µm are formed on planes with @phi@ = 45 n° ± 15° (n = 1, 3, 5, 7).