Basaran, Engin (1995) The MBE growth and electrical characterisation of high resolution doped Si/GeSi structures. PhD thesis, University of Warwick.

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Abstract

Exploring the properties and physical limits of nanometer scale
structures and devices, emerged with the advent of epitaxial techniques such
as Molecular Beam Epitaxy (MBE). This has correspondingly created
challenges to the available characterisation techniques. Determination of
carrier concentration profiles in semiconductor structures is of vital
importance since the operation of devices depends on it. Of the commonly
used techniques, conventional capacitance-voltage (CV) has a major
drawback due to the breakdown voltage at high reverse bias particularly at
highly doped structures. The most competitive techniques for carrier
concentration profiling are the electrochemical CV (ECV) which does not
suffer from this limitation, Spreading Resistance Profiling (SRP) and Hall
combined with stripped measurement.
This thesis reports experimental investigations of the capability and
limitations of the ECV technique through comparisons with Secondary Ion
Mass Spectroscopy (SIMS) and SRP on hitherto difficult profiling conditions in
Si and, for the first time, carrier profiling in SilSiGe structures. The ECV
technique is shown to be well capable of profiling Si structures doped with
boron up to the solid solubility limits. It is also demonstrated for the first time
that ECV is better suited to profiling ultra thin boron layers including deltalayers
in Si than the SRP technique. The first attempts to profile boron doped
Si/SiGe structures have revealed that this material system can be depthprofiled
with the electrolytes used to profile Si under optimised conditions,
providing that the Ge concentration is kept below 25%. The importance of
the electrolytes, leakage current, and the models used are also discussed
with specific samples. Also the changes in etch current density between Si
and SiGe enabled Ge profiles to be obtained in Si/SiGe heterostructures.
World record mobilities in strained SiGe channel MBE-grown normal
structures are obtained through the use of very high substrate temperatures
during growth whilst reducing the Ge concentration below 13% and limiting
the thickness of the alloy layer. The theoretical calculations related to
scattering mechanisms suggested that utilising high substrate temperatures
results in reduction of both interface charge and interface roughness
scattering, these being the dominant scattering mechanisms in the present
material system.

Item Type:	Thesis (PhD)
Subjects:	Q Science > QC Physics
Library of Congress Subject Headings (LCSH):	Doped semiconductors -- Analysis, Nanotechnology, Molecular beam epitaxy
Official Date:	March 1995
Dates:	Date Event March 1995 Submitted
Institution:	University of Warwick
Theses Department:	Department of Physics
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Kubiak, R. A.
Sponsors:	Ondokuz Mayıs Üniversitesi
Extent:	xiii, 139 p.
Language:	eng

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