Final answer:
In a PN junction under forward bias, the width of the depletion region becomes thinner than at equilibrium, which lowers the potential energy barrier height, allowing for an increased flow of electric current.
Step-by-step explanation:
Description of PN Junction in Forward Bias
When a PN junction is forward-biased, the positive terminal of the battery is connected to the p-type material and the negative terminal to the n-type material. This configuration reduces the width of the depletion region and lowers the potential energy barrier that restricts the movement of charge carriers. Consequently, the electric field produced by the uncovered ions at the junction, which normally opposes the diffusion of charge carriers, is weakened, allowing more carriers to cross the junction. The result is an increase in the flow of electric current across the junction.
Regarding the question posed, the depletion region under forward bias is thinner than at equilibrium. This is because the external voltage applied reduces the built-in potential across the PN junction, hence decreasing the barrier height and the depletion width.
Impact on Energy Barrier and Depletion Region
The energy barrier height is reduced as the built-in potential barrier is opposed by the external bias voltage. The slope of the energy bands at the PN junction becomes less steep as well, indicating a lowered barrier for charge carriers. The depletion region width becomes thinner, enabling an easier flow of carriers, which in turn, increases the forward current.