Location of donor atom electrons in N-type Silicon

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SUMMARY

The discussion clarifies the placement of donor atom electrons in N-type silicon semiconductors. It establishes that while the region between the top of the valence band (VB) and the bottom of the conduction band (CB) is termed the "forbidden gap," doping introduces additional energy levels within this gap. Specifically, the extra electrons from donor atoms occupy energy levels just below the conduction band, contradicting the notion that nothing exists in the forbidden gap. This distinction is crucial for understanding solid-state electronics and semiconductor behavior.

PREREQUISITES
  • Understanding of energy band diagrams in semiconductors
  • Knowledge of N-type and P-type semiconductor concepts
  • Familiarity with doping processes in solid-state physics
  • Basic principles of solid-state electronics
NEXT STEPS
  • Research the energy band structure of P-type semiconductors
  • Study the effects of different doping materials on semiconductor properties
  • Learn about the role of the forbidden gap in electronic devices
  • Explore the principles of charge carrier mobility in semiconductors
USEFUL FOR

Students and professionals in solid-state electronics, semiconductor physicists, and anyone seeking to deepen their understanding of N-type semiconductor behavior and energy band theory.

CoolDude420
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I'm taking a module in solid state electronics and I'm a bit confused with the energy band diagrams. I was told that the region between the top of VB and and the bottom of the CB is the "forbidden gap". However after learning about N-type semiconductors(silicon), I see that the extra electron from the donor atoms have their own energy level right below the bottom of the conduction band in the so called "forbidden gap". How can this be? I'm quite new to solid state and all of its terminology so any help is appreciated.

Heres a pic: [cant post pic]. its the first one on this page
http://hyperphysics.phy-astr.gsu.edu/hbase/solids/dsem.html#c2

dban2.gif
 
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The states are produced by the doping atoms. Undoped semiconductors don't have states in the bandgap, but doped semiconductors do.
 
mfb said:
The states are produced by the doping atoms. Undoped semiconductors don't have states in the bandgap, but doped semiconductors do.

Shouldn't they be in the VB though? Since nothing is meant to be in the Forbidden Gap
 
CoolDude420 said:
Since nothing is meant to be in the Forbidden Gap
This statement applies to electrons in undoped semiconductors only. It does not apply to modifications of the crystal.

"I cannot put an apple in a box because there is no box."
"Here I give you a box"
"Now I can put an apple in a box."
 

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