X-ray studies of gallium arsenide-silicon heterostructures
Lucas, Norene Gayle
This item is only available for download by members of the University of Illinois community. Students, faculty, and staff at the U of I may log in with your NetID and password to view the item. If you are trying to access an Illinois-restricted dissertation or thesis, you can request a copy through your library's Inter-Library Loan office or purchase a copy directly from ProQuest.
Permalink
https://hdl.handle.net/2142/29199
Description
Title
X-ray studies of gallium arsenide-silicon heterostructures
Author(s)
Lucas, Norene Gayle
Issue Date
1993
Doctoral Committee Chair(s)
Zabel, Hartmut
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
gallium arsenide-silicon
GaAs
x-ray scattering
Language
en
Abstract
Gallium arsenide-silicon heterostructures combine complementary electronic and
structural properties to greater technological potential. The large 4% mismatch in lattice
parameter between the two semiconductors strongly affects disorder within the film
and at the interface. We employ x-ray scattering to explore the structural properties of
these layered materials grown by molecular beam epitaxy.
The thermal expansion of thick GaAs films on nominal Si(001) is measured with x-ray
diffraction. The gallium arsenide film exhibits an anisotropy between the in-plane and outof-
plane lattice parameters due to the large thermal mismatch and the interfacial constraint.
Thick films are found to be strain-free at the growth temperature and expanded in-plane at
room temperature. This contrasts with the in-plane room-temperature contraction shown
in thin films due to the residual strain present during growth.
Interface roughness in thin gallium arsenide films (a few hundred angstroms thick) on
silicon substrates is measured with x-ray reflectivity. The roughness at the GaAs/Si interface
is found to be approximately 9A for a (001) orientation miscut by 4°. Ex situ in vacuo
annealing just below the growth temperature, while reducing both film disorder and the
roughness of the GaAs surface, does not substantially reduce interface roughness. Slow
heating just above the growth temperature degrades the overall film quality.
We also study interface roughness in GaAs films grown on very thin films of Si on
a GaAs substrate. The silicon thickness ranges from pseudomorphic (that is, in-plane
lattice parameter matching the underlying GaAs) to non-pseudomorphic. The GaAs/Si
interface roughness increases from approximately 5A for the thinnest Si interlayer. The
GaAs surface roughness increases dramatically at about the critical film thickness. But the onset of increased surface roughness occurs well before the Si thickness approaches critical
and before the onset of increased interface roughness.
Use this login method if you
don't
have an
@illinois.edu
email address.
(Oops, I do have one)
IDEALS migrated to a new platform on June 23, 2022. If you created
your account prior to this date, you will have to reset your password
using the forgot-password link below.
