PN Junction. Silicon vs Germanium

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SUMMARY

The discussion focuses on the differences between silicon and germanium in PN junctions, specifically regarding their barrier potentials. At 25°C, silicon exhibits a barrier potential (Vbp) of 0.7 V, while germanium has a lower Vbp of 0.3 V. This discrepancy arises despite germanium's electrons having more energy due to its atomic structure, which allows for easier electron drift from the N region to the P region. The potential difference is influenced more by factors such as the dielectric constant of the semiconductors and the effective mass of charge carriers rather than merely the number of valence electrons.

PREREQUISITES
  • Understanding of semiconductor physics
  • Knowledge of P-type and N-type doping
  • Familiarity with barrier potential concepts
  • Basic principles of charge carrier dynamics
NEXT STEPS
  • Research the dielectric constant of silicon and germanium
  • Study the effective mass of charge carriers in semiconductors
  • Explore the impact of temperature on semiconductor behavior
  • Learn about the applications of PN junctions in electronic devices
USEFUL FOR

This discussion is beneficial for electrical engineers, semiconductor physicists, and students studying materials science, particularly those interested in the properties and applications of silicon and germanium in electronic components.

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When we connect P and N materials, electrons from N drift to P, thus create negative ions in P and positive ions in N.

=> electric field (barrier potential) must depend on an amount of electrons recombined with holes in P region.

=> The more electrons recombined, the more ions created, the more barrier potential.

BUT! Silicon has 14 electrons and 4 on the 3d shell. Germanium has 32 electrons and 4 on the 4th shell.

=> at 25C degrees, electrons in N region in Germanium must have more energy than electrons in Silicon, because less energy required to remove electron from an atom => more electrons can drift to P region, thus barrier potential for Germanium should be higher, however

Vbp Germanium = 0.3 V Vbp Silicon = 0.7 V

why?

P.S. I am talking about P doped and N doped silicon compared to the junction between P doped and N doped germanium
 
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The number of electrons which recombine does not depend on the number of valence electrons. The potential difference rather depends on things like the dielectric constant of the semiconductors and the effective mass of the charge carriers.
 
Thanks DrDu!
 

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