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. Recombination occurs when a free electron collides with a hole, annihilating both and releasing energy, balancing the generation rate at equilibrium. Substituting values gives Reduces free carriers, which matches expected behaviour for this semiconductor device configuration, confirming doping, depletion and rectifier principles.