Growth, microstructure, and strain relaxation in low-temperature epitaxial Si{sub 1{minus}{ital x}}Ge{sub {ital x}} alloys deposited on Si(001) from hyperthermal beams
- Materials Science Department, the Coordinated Science Laboratory, and the Materials Research Laboratory, University of Illinois, 1101 West Springfield Avenue, Urbana, Illinois 61801 (United States)
Epitaxial Si{sub 1{minus}{ital x}}Ge{sub {ital x}}(001) alloy films, with 0.15{le}{ital x}{le}0.30, were grown on Si(001) at temperatures {ital T}{sub {ital s}} ranging from 300 to 550{degree}C using hyperthermal Si (average energy {l_angle}{ital E}{sub Si}{r_angle}{approx_equal}18 eV) and Ge ({l_angle}{ital E}{sub Ge}{r_angle}{approx_equal}15 eV) beams. The deposition rate was 0.1 nms{sup {minus}1} and film thicknesses ranged from 30 nm to 0.8 {mu}m. The energetic Si and Ge beams are generated by bombarding Si and Ge targets with 1 keV Kr{sup +} ions from double-grid, multiaperture, broad ion-beam sources in a system geometry established based upon TRIM simulations of energy-dependent angular distributions of sputtered and backscattered particles. A combination of high-resolution plan-view and cross-sectional transmission electron microscopy, high-resolution x-ray diffraction, Rutherford backscattering spectroscopy, channeling, and axial angular-yield profiles demonstrated that the films are of extremely high crystalline quality. Critical layer thicknesses {ital h}{sub {ital c}} for strain relaxation in these alloys were found to increase rapidly with decreasing growth temperature. For Si{sub 0.70}Ge{sub 0.30}, {ital h}{sub {ital c}} ranged from 35 nm at {ital T}{sub {ital s}}=550{degree}C to 650 nm at 350{degree}C compared to an equilibrium value of {approx_equal}8 nm. At even lower growth temperatures, {ital h}{sub {ital c}} becomes larger than critical epitaxial layer thicknesses, {approx_gt}1 {mu}m at 300{degree}C. In addition, atomic force microscopy studies showed that strain-induced roughening, which occurs at elevated growth temperatures, is strongly suppressed at {ital T}{sub {ital s}} between 300 and 400{degree}C with no indication of kinetic roughening. {copyright} {ital 1996 American Institute of Physics.}
- Research Organization:
- Univ. of Illinois at Urbana-Champaign, IL (United States)
- DOE Contract Number:
- AC02-76ER01198
- OSTI ID:
- 285543
- Journal Information:
- Journal of Applied Physics, Vol. 80, Issue 2; Other Information: PBD: Jul 1996
- Country of Publication:
- United States
- Language:
- English
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