Compositional modulations in Ge/sub x/Si/sub 1-//sub x/ heteroepitaxial layers

Journal Article · Wed Mar 01 00:00:00 EST 1989 · J. Vac. Sci. Technol., B; (United States)

DOI:https://doi.org/10.1116/1.584718· OSTI ID:6335021

Fraser, H L; Maher, D M; Knoell, R V; Eaglesham, D J; Humphreys, C J; Bean, J C

A study is presented of compositional modulations (i.e., so-called banding) in heteroepitaxial strained layers of nominally uniform Ge/sub 0.1/Si/sub 0.9/ grown by molecular-beam epitaxy (MBE). The oscillatory nature of the modulations is studied by transmission electron microscopy (TEM) techniques and the results show that the contrast modulations have a periodicity of /similar to/23 nm when 1-..mu..m-thick epilayers are grown on a rotated substrate. For growth on an unrotated substrate, contrast modulations are still observed but they are less regular. It is further shown that the electron microscope image features are dominated by strain contrast and not structure factor contrast. The presence of strain is consistent with there being a small change in lattice parameter between adjacent bands of material, together with elastic relaxations afforded by the proximity of the thin-film surfaces. It is concluded that these variations in the lattice parameter are due to the compositional modulations. Limits on the magnitude (..delta..x) of the compositional modulations are assessed from considerations of diffraction contrast theory (giving an upper limit) and elasticity theory (giving a lower limit). The upper and lower limits for the compositional modulations, assuming an average 9 at. % Ge--Si epilayer, are +- 1 at. % and +- 0.25 at. % Ge, respectively. The origin of these compositional modulations is thought to be associated with equipment instabilities or a metastable miscibility gap.

• Research Organization: University of Illinois, Urbana-Champaign, Illinois 61801
• OSTI ID: 6335021
• Journal Information: J. Vac. Sci. Technol., B; (United States), Vol. 7:2
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
GERMANIUM ALLOYS
CHEMICAL VAPOR DEPOSITION
SILICON
COATINGS
SILICON ALLOYS
CHEMICAL COMPOSITION
CRYSTAL STRUCTURE
EXPERIMENTAL DATA
HETEROJUNCTIONS
LAYERS
SUBSTRATES
TRANSMISSION ELECTRON MICROSCOPY
ALLOYS
CHEMICAL COATING
DATA
DEPOSITION
ELECTRON MICROSCOPY
ELEMENTS
INFORMATION
JUNCTIONS
MICROSCOPY
NUMERICAL DATA
SEMICONDUCTOR JUNCTIONS
SEMIMETALS
SURFACE COATING
360602* - Other Materials- Structure & Phase Studies