Extra exam question E6A03

WhyA PN-junction diode doesn't conduct when reverse biased because the applied voltage separates the holes in the P-type material and the electrons in the N-type material, widening the depletion region. When a PN-junction diode is reverse biased, the applied voltage pulls the majority carriers, holes in the P-type material and electrons in the N-type material, away from the junction, widening the depletion region and leaving essentially no charge carriers available to support current flow across it, answer C. It isn't that only one type of material can conduct, and reverse bias doesn't cause carriers to recombine and turn the whole diode into an insulator, the blocking action comes specifically from that widened, carrier-depleted region.