Visible luminescence from porous silicon

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(?ext) of
  PS LEDs
• ?ext a ?int ?inj ?extract
• ?int for PS is relatively high( about 10)
• For increasing ?inj n type is being used
• ?extract 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 its good sensitivity and very large
surface
9

• References
• Website http//ee.tamu.edu/ryongkim/webafm/topv
  iew.html.
• El-Bahar, A. and Nemirovsky, Y., Appl. Phys.
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• 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).