In reverse biasing, the positive terminal of battery is connected to n-type semiconductors and negative of the battery is connected to p-type material of the p-n junction. As a result the holes in p-section and electrons in n-section move away from the junction with the result that the barrier layer is thickened leaving only a few thermally generated majority carriers to produce very small current. If we go on increasing the reverse bias, the temperature of p-n junction increases and this rise in temperature enhances the minority carrier concentration and the current increases rapidly. Beyond this limit, called zener voltage, the voltage across the junction remains constant for a large current.
