Semiconductor physics: Voltage below forward voltage

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Discussion Overview

The discussion revolves around the behavior of a diode in a closed circuit when subjected to a voltage below its forward voltage. Participants explore the implications of this scenario on charge carrier dynamics, depletion region characteristics, and potential energy changes within the semiconductor material, specifically silicon.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant describes a scenario where a diode is connected in reverse, questioning the movement of electrons and the formation of bonds with boron atoms due to insufficient voltage to create free charge carriers.
  • Another participant suggests viewing the situation as analogous to the narrowing of the depletion layer, similar to how reverse bias widens it, proposing that work is done in this context.
  • A different participant challenges the idea of narrowing the depletion region, arguing that increased voltage leads to higher drift velocities of free electrons, which could affect the depletion region differently.
  • One participant expresses a lack of data regarding the capacitance of a varactor diode under forward bias, indicating a potential area for further investigation.
  • Another participant indicates an intention to conduct personal experiments to gather more information on the topic.

Areas of Agreement / Disagreement

Participants express differing views on the behavior of the depletion region under low voltage conditions, with no consensus reached on the implications of these dynamics or the effects on charge carriers.

Contextual Notes

Participants mention various assumptions regarding the behavior of charge carriers and the depletion region, but these assumptions remain unresolved and depend on specific conditions and definitions related to semiconductor physics.

Who May Find This Useful

This discussion may be of interest to individuals studying semiconductor physics, particularly those focused on diode behavior, charge carrier dynamics, and experimental approaches to understanding these phenomena.

CaptainMarvel1899
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Assume we have a diode closed circuit.We connect the p type region of the diode to the positive terminal of the battery(cathode).We connect the n type region of the diode to the negative terminal of the battery(anode).The voltage of the battery is 0.3V .The diode%s intristic se miconductor is silicon.Here is my issue . The net force moves the electrons from the n type to the p type.But because there is not enough voltage the valence electrons of silicon have a slight propability to overcome the band gap and become free charge carriers.But if they don't become become free charge carriers they will form bonds with B-atoms because charges do move and fill Boron holes.And this would result to a bigger potential energy of the system.What am I missing?
 
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Can you not just look at it as narrowing the depletion layer - in the same way that reverse bias will widen it? Work will have been done because the unbiased condition will be the lowest Energy situation.
 
H
sophiecentaur said:
Can you not just look at it as narrowing the depletion layer - in the same way that reverse bias will widen it? Work will have been done because the unbiased condition will be the lowest Energy situation.
Widening of the depletion region in reverse bias does happen.Narrowing doesn't happen as you think it is happening.As voltage is increased the drift velocity of the free electrons is increased so they switch on and off the depletion region more frequently if the had less voltage , so less resistance.Also the depletion region is decreased by the applied voltage because electrons gain energy due to the the electric potential and have a bigger propability of becoming free charge carriers.So back to my question how do you explain this thing maybe the depletion region would be increased(not very much)by the movement of those carriers?
 
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Likes   Reactions: sophiecentaur
Idid a quick search but could find no data about the Capacitance of a varactor diode under forward bias. That would give a clue??
 
Yes it gives me a clue.I will do some experiments on my own and tell you the results.
 

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