Electrical Transport Studies of Electro Optically Active Semiconductors

1. 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

2. Overview • Motivation • Background • Work to be performed • Sample Preparation • Anticipated Results • Anticipated Timeline • Summary

3. 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.

4. Background Direct bandgap semiconductors are efficient for optical emission properties. Indirect Bandgap transition Direct Bandgap transition

5. Background Silicon Bulk silicon has an indirect energy bandgap and is therefore highly inefficient as light source. GaAs GaAs has a direct band gap.

6. Band Structure Silicon Band structure GaAs Band structure

7. Why β-Fesi2? • It exhibits quasi direct bandgap around 0.8eV corresponding to 1.5μm wavelength.

8. β-Fesi2 band structure

9. β-Fesi2 • Light emission has been observed only in strained • films of β-Fesi2.An alternative to strain is band structure • modification by alloying.

10. Crystal Structure of GaAsSb

11. Ordering in III-V Semiconductor alloys

12. Reduction in the Band Gap

13. Characterization techniques • Electrical Magneto transport technique. • Optical • Transmission measurements like absorption co-efficient and photoluminescence. • Electro-Optical • Photocurrent measurements.

14. Magneto Transport Technique • Hall Effect Hall effect sign conventions for n-type sample Hall effect sign conventions for p-type sample

15. Hall Effect Hall Coefficient RH:   RH =VHt/(BI) Conductivity: σ = I l/(VA ) Mobility: µ=σ RH

16. 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 • Studying the electrical characteristics of β-Fesi2 as a function of different dosages and implantation energies of ions.

17. Sample No Substrate orientation % Sb from XRD IC 479 (001) 66.9 IC 480 (001) 8˚ towards (111)A 65 Work To Be Performed • Examining the anisotropic properties of GaAsSb as a function of the degree of ordering.

18. 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.

19. Equipment Available • Electrical characterization High Field Cryostat. Sample with contacts Sample Holder

20. Equipment Available Magnets used for Magneto Transport Characteristics

21. 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

22. Activity Timeline in Months 1 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 Anticipated Timeline

23. 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.