What Causes the Depletion Region?

Answer: Charge diffusion is what creates the depletion area. Due to the concentration gradient, holes diffuse across the junction from a p-side to an n-side, whereas electrons diffuse in the opposite direction from an n-side to a p-side. Near the junction, the holes and the electrons diffusely move in almost the same direction. Positive and negative ions were created as a result. A pair of positive and negative ions make the dipole at the junction. The depletion region is the area containing the dipoles and is devoid of mobile charge carriers.