Practice question

**Depletion region** also called space-charge region, thickness typically 0.5 μm, contains no mobile carriers, only fixed ions, negative on p-side, positive on n-side, diffusion current due to concentration gradient, drift current due to field, equilibrium when J_drift + J_diff =0, voltage drop mainly across depletion region. Diffusion current arises from the movement of carriers (holes from p-side to n-side, electrons from n-side to p-side) due to concentration gradients across the junction during its formation. Substituting values gives Concentration gradient, which matches expected behaviour for this semiconductor device configuration, confirming doping, depletion and rectifier principles.