Drift vs Diffusion current

In summary: Can someone please provide a reference link or a summary of the information so that I can understand it better?In summary, the potential barrier decreases, allowing more majority carriers from one side to diffuse to the other side where they are minority carriers. After they cross the potential barrier, they form a diffusion current, the drift current of minority carriers is insignificant, then they recombine with majority carriers and form a drift current under the effect of the applied electric field.
  • #1
Amerez
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In a forward-biased PN junction, the potential barrier decreases, allowing more majority carriers from one side to diffuse to the other side where they are minority carriers. After they cross the potential barrier, they form a diffusion current, the drift current of minority carriers is insignificant, then they recombine with majority carriers and form a drift current under the effect of the applied electric field.

Why do minority carriers form a diffusion current not a drift current after they cross the potential barrier? It is counter-intuitive that the main current is diffusion when there is an applied electric field.

This is according to all the microelectronics book I'm currently reading. There is one which says this can be proved but without providing anything. Can someone please provide a proof for this.
 
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  • #2
This is a good read on Transistor Action.

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  • #3
I have went through the link you provided, but this doesn't touch on the question.
Maybe this thread is more solid-state physics than electrical engineering !?
 
  • #5
maybe you'd like to borrow a book :-p
 

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  • #6
lol, it may be the only way.
I'm actually reading through Sedra 5th edition on this matter, it states the current is a diffusion current but without giving the reasons. It seems electrical engineering books leave many holes when describing the physics of the devices
 
  • #7
Amerez said:
I have went through the link you provided, but this doesn't touch on the question.
Maybe this thread is more solid-state physics than electrical engineering !?
You went through all that? Did you go through their links

Semiconductor concepts and Semiconductors for electronics
 
  • #8
dlgoff said:
You went through all that? Did you go through their links

Semiconductor concepts and Semiconductors for electronics

Yes, I've been scanning this site for the past couple of weeks.
Most of the sites I've read seem to describe the operation of the PN junction or the diode, but I'm unable to find the answer to this specificity.
 

Related to Drift vs Diffusion current

What is the difference between drift and diffusion current?

Drift and diffusion current are two types of charge transport mechanisms in a material. Drift current refers to the movement of charge carriers due to an applied electric field, while diffusion current is caused by the concentration gradient of charge carriers. In other words, drift current is a result of an external force, while diffusion current is a result of internal forces within the material.

How are drift and diffusion current related to each other?

Drift and diffusion current are interdependent and work together to maintain the equilibrium of charge carriers in a material. The drift current generates an electric field, which in turn affects the concentration gradient of charge carriers and leads to a diffusion current.

Which type of current dominates in different materials?

The dominance of drift or diffusion current depends on the material's properties. In materials with high conductivity and low carrier mobility, such as metals, drift current is dominant. In contrast, materials with low conductivity and high carrier mobility, such as semiconductors, have a higher diffusion current.

How does temperature affect drift and diffusion current?

Increasing the temperature of a material generally increases both drift and diffusion current. This is because higher temperatures lead to higher thermal energy and more collisions between charge carriers, resulting in a higher drift velocity and a larger diffusion coefficient.

How are drift and diffusion current utilized in electronic devices?

Drift and diffusion current play a crucial role in the operation of electronic devices, such as transistors and diodes. The control of these currents allows for the manipulation of charge carriers and the flow of electricity, enabling the functioning of these devices.

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