electrical transport studies of electro optically active semiconductors master’s thesis proposal...
TRANSCRIPT
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Electrical Transport Studies of Electro Optically Active Semiconductors
Master’s Thesis Proposal
Committee MembersDr.Terry Golding
Dr. Roman StemprokDr. Mitty Plummer
Presented By Srikala Kambhampati
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Overview
• Motivation
• Background
• Work to be performed
• Sample Preparation
• Anticipated Results
• Anticipated Timeline
• Summary
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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.
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Background Direct bandgap semiconductors are efficient for optical emission properties.
Direct Bandgap transition Indirect Bandgap transition
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Background
Silicon
Bulk silicon has an indirect energy bandgap and is therefore highly inefficient as light source.
GaAs
GaAs has a direct band gap.
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Band Structure
Silicon Band structure GaAs Band structure
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Why β-Fesi2?
• It exhibits quasi direct bandgap around 0.8eV corresponding to 1.5μm wavelength.
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β-Fesi2 band structure
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•Light emission has been observed only in strained films of β-Fesi2.An alternative to strain is band structure modification by alloying.
β-Fesi2
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Crystal Structure of GaAsSb
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Ordering in III-V Semiconductor
alloys
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Reduction in the Band Gap
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Characterization techniques
• Electrical
Magneto transport technique.
•Optical
Transmission measurements like absorption co-efficient and photoluminescence.
•Electro-Optical
Photocurrent measurements.
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Magneto Transport Technique
• Hall Effect
Hall effect sign conventions for p-type sample
Hall effect sign conventions for n-type sample
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Hall Effect
Hall Coefficient RH:
RH =VHt/(BI)
Conductivity:
σ = I l/(VA )
Mobility:
µ=σ RH
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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
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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
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Sample Preparation
Silicides• Molecular Beam Epitaxy by W.Henrion, Hahn-Meitner-
Institut 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.
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Equipment Available
• Electrical characterizationHigh Field Cryostat.
Sample HolderSample with contacts
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Magnets used for Magneto Transport Characteristics
Equipment Available
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Anticipated Results
• 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
β-Fesi2
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Anticipated TimelineActivity
Timeline in Months1 2 3 4 5 6 7 8 9 10 11 12
Review of Literature
Sample Preparation Experimentati-on and Analysis of Results
Documentation and write-Up
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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.