Final answer:
Diffusion current in a p-n junction flows from the p-side to the n-side when forward biased and is restricted in reverse bias. A semiconductor diode allows current to flow in only one direction, acting as a one-way valve. The behavior is described by the Maxwell-Boltzmann distribution and external potential influence.
Step-by-step explanation:
The diffusion current in a p-n junction varies depending on whether the junction is forward or reverse biased. In a forward biased junction, the diffusion current flows from the p-side to the n-side because the depletion layer narrows, reducing the potential energy barrier, which allows for easier flow of electrons (and holes). Conversely, in a reverse bias setup, the positive terminal of the battery is connected to the n-side, widening the depletion layer, increasing the potential energy difference across the junction, and severely restricting the flow of majority carriers, which effectively reduces the diffusion current.
A semiconductor diode operates on this principle, only allowing current to flow readily in the forward bias configuration, while significantly impeding it in reverse bias. Therefore, the diode acts as a one-way valve for electrical current. The behavior of the diode under different biases can be described through concepts such as the Maxwell-Boltzmann distribution and the influence of an external potential on the movement of charge carriers across a p-n junction.