Final answer:
The width of the depletion region in a pn junction decreases as the doping concentration is increased due to a stronger electric field resulting from the increased charge density.
Step-by-step explanation:
The depletion region of a pn junction varies inversely with the doping concentration. When the doping concentration is increased, the number of charge carriers (electrons in n-type and holes in p-type material) increases. This leads to a higher charge density near the pn junction, which in turn results in a stronger electric field.
In equilibrium, when the diffusion and drift currents are balanced, the depletion region width is determined by the balance between the uncovered fixed charges and the electric field. If doping is increased, the electric field strengthens more rapidly because more fixed ions are uncovered.
This causes the depletion region to become narrower, thereby reducing its width. Conversely, if doping concentration is decreased, there are fewer fixed ions, leading to a weaker electric field and a wider depletion region.
It is important to note that the width of the depletion region affects the behavior of semiconductor devices like diodes. In the reverse bias configuration, increasing the doping concentration will make the depletion region thinner and could reduce the potential barrier height.
In the forward bias configuration, a thinner depletion region means that less voltage is needed to overcome the potential barrier, allowing charge carriers to cross the junction more readily.