P-N Junction ‒ Reverse Bias

When an external voltage is applied to a diode as shown in the model — with the positive terminal connected to N-type material and the negative terminal connected to P-type material — this voltage causes the movement of electrons and holes within the P-N junction. Electrons from the wire connected to the negative terminal are injected into the P-type material, depleting the holes further and causing the depletion layer to widen. A similar effect occurs on the other side, where the positive terminal pulls electrons from the N-type material. The overall effect is that the external voltage causes the barrier voltage of the P-N junction to oppose the external voltage. Any initial charge movement due to the applied voltage will only increase this barrier voltage, preventing current from flowing through the diode. A diode connected with this polarity is referred to as reverse biased.