# Drift velocity in P-N Junctions

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• nickhobbs
In summary, when a P-N junction is in reverse bias, there is a small reverse current due to the strong electric field in the depletion region which sweeps out any charge carriers present. The reverse current is only weakly dependent on the reverse voltage.
nickhobbs
When a P-N junction is in reverse bias, the drift velocity of the system increases, so why is there no current flow? Is the drift velocity not connected to the current?

nickhobbs said:
When a P-N junction is in reverse bias, the drift velocity of the system increases, so why is there no current flow? Is the drift velocity not connected to the current?

pl. explain how the drift velocity increases in a biased p-n junction.
moreover Is the current dependent on drift velocity if a voltage is applied?

drvrm said:
pl. explain how the drift velocity increases in a biased p-n junction.
moreover Is the current dependent on drift velocity if a voltage is applied?
In the depletion zone (when in reverse bias) there is a steeper potential gradient and so the drift current increases?

I thought the current was dependent on the drift velocity

drvrm
nickhobbs said:
When a P-N junction is in reverse bias, the drift velocity of the system increases, so why is there no current flow?
Actually, there is a current flowing. It is called reverse current and it is only weakly dependent on the reverse voltage.
The field in the depletion region of a p-n junction is quite strong and if you reverse bias the junction, any charge carrier within that region will be swept out immediately. Therefore, the reverse current depends on rate of carrier generation within the depletion region.

## 1. What is drift velocity in P-N junctions?

Drift velocity in P-N junctions refers to the speed at which charged particles move through a semiconductor material when an electric field is applied to a P-N junction. This movement of charged particles is responsible for creating a current flow within the junction.

## 2. How is drift velocity calculated?

Drift velocity can be calculated using the formula v = μE, where v is the drift velocity, μ is the mobility of the charged particles, and E is the electric field strength. The mobility is a material-specific constant that describes how easily charged particles can move through a material.

## 3. What factors affect drift velocity in P-N junctions?

The drift velocity in P-N junctions can be affected by several factors, including the strength of the electric field, the mobility of the charged particles, and the temperature of the material. Additionally, the presence of impurities or defects in the semiconductor material can also impact the drift velocity.

## 4. Why is drift velocity important in P-N junctions?

Drift velocity is important in P-N junctions because it is directly related to the current flow within the junction. By understanding and controlling the drift velocity, scientists and engineers can manipulate the flow of current and design more efficient electronic devices.

## 5. How does drift velocity change in a forward-biased and reverse-biased P-N junction?

In a forward-biased P-N junction, the drift velocity increases as the electric field strength increases. However, in a reverse-biased P-N junction, the drift velocity remains relatively constant regardless of the electric field strength. This is because the majority carriers in a forward-biased junction are pushed towards the junction, increasing the drift velocity, while in a reverse-biased junction, the majority carriers are pushed away from the junction, resulting in a constant drift velocity.

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