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 Holder Sample 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.