Silicon, Circuits, and the Digital Revolution

Concentration of Doping - Semiconductors into Metals

• Review effects of doping on resistivity of semiconductor
  -- figure from Ashcroft and Mermin "Solid State Physics" showing antimony-doped germanium

  Donor Concentration	Resistivity
  (micropercent)	(ohm-cm)
  5	109
  50	105
  150	10
  300	0.1

• the first factor of ten increase in doping leads to a factor of ten-thousand increase in conductivity!
• For comparison, this is like a return of $2 on a $1 investment, shooting up to a $20,000 return on increasing to a $10 investment...
• a factor of 60 variation in doping level results in ten orders of magnitude variation in resistivity.
• converts germanium effectively into a metal!

Comments, suggestions, or requests to ghw@udel.edu. "http://www.physics.udel.edu/~watson/scen103/colloq2000/doping-concentration.html" Last updated April 20, 2000. © George Watson, Univ. of Delaware, 2000.