The width of the space charge region at a p-n junction is reduced by applying a voltage bias over the p-n junction. What is the correct statement on both the bias voltage and the p-n junction?
The voltage is a forward bias and the diffusion of the majority charge carriers becomes more dominant.
The voltage is a reverse bias and the diffusion of the majority charge carriers becomes more dominant.
The voltage is a forward bias and the drift of the minority charge carriers becomes more dominant.
The voltage is a reverse bias and the drift of the minority charge carriers becomes more dominant.
To determine the correct statement, we need to understand what happens at a p-n junction and how voltage bias affects it.
A p-n junction is formed by bringing together a p-type semiconductor (with an excess of holes as majority charge carriers) and an n-type semiconductor (with an excess of electrons as majority charge carriers). At the junction, diffusive processes occur, where holes diffuse from the p-region to the n-region, and electrons diffuse from the n-region to the p-region. This gives rise to a region called the space charge region or depletion region.
Applying a voltage bias to the p-n junction means connecting a voltage source across the junction. There are two types of voltage bias: forward bias and reverse bias.
In forward bias, the positive terminal of the voltage source is connected to the p-side, and the negative terminal is connected to the n-side. This attracts the majority charge carriers (holes in the p-region and electrons in the n-region) towards the junction, reducing the width of the space charge region. In this bias condition, the diffusion of the majority charge carriers becomes more dominant.
On the other hand, in reverse bias, the positive terminal of the voltage source is connected to the n-side, and the negative terminal is connected to the p-side. This repels the majority charge carriers away from the junction, increasing the width of the space charge region. In reverse bias, the drift of the minority charge carriers (holes in the n-region and electrons in the p-region) becomes more dominant.
Therefore, the correct statement is:
The voltage is a forward bias and the diffusion of the majority charge carriers becomes more dominant.