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Visible luminescence from porous silicon

Visible luminescence from porous silicon. Samad bazargan Sharif University of Technology Department of Physics. May 31,2003. Porous Silicon. Anodizing Electrochemically or Chemically in an HF-containing electrolyte:

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Visible luminescence from porous silicon

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  1. Visible luminescence from porous silicon Samad bazargan Sharif University of TechnologyDepartment of Physics May 31,2003

  2. Porous Silicon • Anodizing Electrochemically or Chemically in an HF-containing electrolyte: 1) Stain etching 2) Anodization

  3. Properties of Porous Silicon • Photoluminescence • Half width of luminescence band can be appreciably narrower than band width of device quality (~0.1 ev).(4) • Etching time and concentration Such band-gap luminescence is not consequence of alloying effect but quantum size effect(4) Increasing porosity and decreasing size with more time and concentration

  4. Excitation energy Photons with higher energy excite thinner wires There is a size distribution

  5. n-type or p-type wire sizes • Passivation of surface recombination centers increases PL intensity Oxidation Being hydrated Deposition of Nitride(5)

  6. Visible Electroluminescence • Electric current make Si glow Red • Substitute for Costly GaAs in LEDs • Power efficiency of 0.1% but external quantum efficiency of more than 1% because of their high turn on voltage

  7. Increasing external quantum efficiency(ηext) of PS LED’s: • ηext αηintηinjηextract • ηint for PS is relatively high( about 10%) • For increasing ηinj n+ type is being used • ηextract depend on geometry and refractive index of system

  8. PS is still research concern of scientists and engineers because of wide and interesting applications of it, such as : • Biosensors and Gas Sensors • Nanocrystalline, porous silicon as the basis for economical flat displays(6) Because of it’s good sensitivity and very large surface

  9. References : • Website: http://ee.tamu.edu/~ryongkim/webafm/topview.html. • El-Bahar, A. and Nemirovsky, Y., Appl. Phys. Lett. 77, 208 (2000). • Murayama,K. ,Komatsu,H., Miyazaki,S., Hirose,M., Solid State Communications, Vol103,No. 3,pp. 155-160(1997). • L. T. Canham, Appl. Phys. Lett. 57, 1046 (1990). • Daami,A., Bermond,G., Stalmans,L., Poortmans,J., Journal of Luminescence 80169-172(1999). • Website: http://www.stp-gateway.de/ • Coulthard,I., Jiang,D.T., Sham,T.K., Journal of Electron Spectroscopy and Related Phenomena 79233-236(1996).

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