Transcript Electrical Transport studies Of Electro Optically Resonant

Electrical Transport Studies of Electro
Optically Active Semiconductors
Master’s Thesis Proposal
Committee Members
Dr.Terry Golding
Dr. Roman Stemprok
Dr. Mitty Plummer
Presented By
Srikala Kambhampati
Overview
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Motivation
Background
Work to be performed
Sample Preparation
Anticipated Results
Anticipated Timeline
Summary
Motivation
• Silicides (β-FeSi2 )
Urgent requirement for an optical emitter that
is compatible with standard silicon based ultra large
scale integration(ULSI) technology.
• III-V Semiconducting materials
Engineering of existing III-V semiconductors
such as GaAsSb.
Background
Direct bandgap semiconductors are efficient for optical
emission properties.
Direct Bandgap transition
Indirect Bandgap transition
Background
Silicon
Bulk silicon has an indirect energy bandgap
and is therefore highly inefficient as light source.
GaAs
GaAs has a direct band gap.
Band Structure
Silicon Band structure
GaAs Band structure
Why β-Fesi2?
• It exhibits quasi direct bandgap around
0.8eV corresponding to 1.5μm wavelength.
β-Fesi2 band structure
β-Fesi2
•Light emission has been observed only in strained
films of β-Fesi2.An alternative to strain is band structure
modification by alloying.
Crystal Structure of GaAsSb
Ordering in III-V Semiconductor
alloys
Reduction in the Band Gap
Characterization techniques
• Electrical
Magneto transport technique.
•Optical
Transmission measurements like absorption coefficient and photoluminescence.
•Electro-Optical
Photocurrent measurements.
Magneto Transport Technique
• Hall Effect
Hall effect sign
conventions for
p-type sample
Hall effect sign
conventions for n-type
sample
Hall Effect
Hall Coefficient RH:
RH =VHt/(BI)
Conductivity:
σ = I l/(VA )
Mobility:
µ=σ RH
Work To Be Performed
• Studying the electrical characteristics of
β-Fesi2 as a function of different dosages and
implantation energies of ions.
Sample No.
substrate
Concentration
Thickness
(opt)
Thickness
(RBS)
344
n-Si(100)
-
251nm
250nm
324
n-Si(111)
XCr=0.01
(EDX)
268 nm
-
358
n-Si(100)
XCr=0.003
(EDX)
-
250nm
367
p-Si(100)
XCo=0.009
(RBS)
282nm
264nm
352
p-Si(100)
XCo=0.066
(RBS)
290 nm
266 nm
353
p-Si(100)
XCo=0.14
(RBS)
307 nm
273 nm
Work To Be Performed
• Examining the anisotropic properties of GaAsSb
as a function of the degree of ordering.
Sample No
Substrate orientation
% Sb from XRD
IC 479
(001)
66.9
IC 480
(001) 8˚ towards (111)A
65
Sample Preparation
Silicides
• Molecular Beam Epitaxy by W.Henrion, Hahn-MeitnerInstitut Berlin GmbH, Berlin, Federal Republic of
Germany, A.G.Birdwell, University of Texas at Dallas,
Texas, U.S.A, V.N.Antonov, Institute of Metal Physics
National Academy of Sciences of Ukraine, Ukraine,
Jepsen, Max-Planck-Institutf ur Festko rperforschung,
Federal Republic of Germany.
GaAsSb
• Molecular Beam Epitaxy at National Renewable Energy
Laboratory by A.G.Norman.
Equipment Available
• Electrical characterization
High Field Cryostat.
Sample Holder
Sample with contacts
Equipment Available
Magnets used for Magneto Transport Characteristics
Anticipated Results
β-Fesi2
• The electrical characteristics of β-Fesi2 material
will be studied for various dosages of ions and
implantation energies.
GaAsSb
• The Electrical anisotropic characteristics of the
samples will be studied for the different degrees of
ordering
Anticipated Timeline
Activity
Timeline in Months
1 2 3 4 5
Review of
Literature
Sample
Preparation
Experimentati
-on and
Analysis of
Results
Documentation
and write-Up
6 7 8 9 10 11 12
Summary
The proposed study of the semi conducting β-Fesi2 and the
anisotropic properties of GaAsSb are presented. The study
of the opto electronic properties of these materials may be
potentially useful in novel device applications.