Explain how a depletion region is formed in p-n junction diode
A p-n junction diode is constructed using a positive and negative semiconductor.
When the two semiconductors are joined, the electrons from the n-side are diffused to the p region and they form a layer of negative charge on the p-side.
Similarly, the positive charges from the p-side are diffused to the n region and they form a layer of positive charge on the n-side.
The region between these two layers is the depletion region of the semiconductor.