Sn-mediated Ge/Ge(001) growth by low-temperature molecular-beam epitaxy: Surface smoothening and enhanced epitaxial thickness

Journal Article · Tue Feb 15 00:00:00 EST 2005 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.1848188· OSTI ID:20668209

Bratland, K A; Foo, Y L; Spila, T; Seo, H -S; Haasch, R T; Desjardins, P; Greene, J E ^[1]

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1. Frederick Seitz Materials Research Laboratory and the Materials Science Department, University of Illinois, 104 South Goodwin Avenue, Urbana, Illinois 61801 (United States)

Fully strained single-crystal metastable Ge{sub 1-x}Sn{sub x} layers were grown on Ge(001) in order to probe the role of Sn dopant and alloy concentrations (C{sub Sn}=1x10{sup 18} cm{sup -3} to 6.1 at. %) on surface roughening pathways leading to epitaxial breakdown during low-temperature (155 deg. C) molecular-beam epitaxy of compressively strained films. The addition of Sn was found to mediate Ge(001) surface morphological evolution through two competing pathways. At very low Sn concentrations (x < or approx. 0.02), the dominant effect is a Sn-induced enhancement in both the Ge surface diffusivity and the probability of interlayer mass transport. This, in turn, results in more efficient filling of interisland trenches, and thus delays epitaxial breakdown. In fact, breakdown is not observed at all for Sn concentrations in the doping regime, 1x10{sup 18}{<=}C{sub Sn}<4.4x10{sup 20} cm{sup -3} (2.3x10{sup -5}{<=}x<0.010){exclamation_point} At higher concentrations, there is a change in Ge{sub 1-x}Sn{sub x}(001) growth kinetics due to a rapid increase in the amount of compressive strain. This leads to a gradual reduction in the film thickness h{sub 1}(x) corresponding to the onset of breakdown as strain-induced roughening overcomes the surface smoothening effects, and results in an increase in the overall roughening rate. We show that by varying the Sn concentration through the dopant to dilute alloy concentration range during low-temperature Ge(001) growth, we can controllably manipulate the surface roughening pathway, and hence the epitaxial thickness, over a very wide range.

• OSTI ID: 20668209
• Journal Information: Journal of Applied Physics, Vol. 97, Issue 4; Other Information: DOI: 10.1063/1.1848188; (c) 2005 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ATOMIC FORCE MICROSCOPY
CRYSTAL GROWTH
DILUTE ALLOYS
FILMS
GERMANIUM
LAYERS
MOLECULAR BEAM EPITAXY
MONOCRYSTALS
MORPHOLOGY
PROBABILITY
SEGREGATION
SEMICONDUCTOR MATERIALS
STRAINS
STRESSES
SURFACES
TEMPERATURE RANGE 0400-1000 K
THICKNESS
TIN
X-RAY DIFFRACTION
X-RAY PHOTOELECTRON SPECTROSCOPY