Electrical Transport Studies of Electro Optically Active Semiconductors
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Transcript of Electrical Transport Studies of Electro Optically Active Semiconductors
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
Overview
• 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
•Light emission has been observed only in strained films of β-Fesi2.An alternative to strain is band structure modification by alloying.
β-Fesi2
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 co-efficient 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-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.
Equipment Available
• Electrical characterizationHigh Field Cryostat.
Sample HolderSample with contacts
Magnets used for Magneto Transport Characteristics
Equipment Available
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
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
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.