Zener diode is used in reverse bias. When its reverse bias is increased, how does the thickness of the depletion layer change?

When a Zener diode is in reverse bias, the thickness of the depletion layer increases as the reverse bias voltage is increased.

A Zener diode is specifically designed to operate in the reverse breakdown region, where it exhibits a phenomenon called the Zener effect. In this region, the diode allows a controlled amount of current to flow in the reverse direction while maintaining a nearly constant voltage across its terminals.

In a Zener diode, the depletion layer plays a crucial role. The depletion layer is formed at the junction between the P-type and N-type semiconductor materials. It consists of immobile ions and creates a barrier for the flow of majority charge carriers (electrons in the P-side and holes in the N-side).

When a reverse bias voltage is applied to the Zener diode, it increases the width of the depletion layer. This occurs due to the electrostatic attraction between the positive terminal of the external power supply and the negative ions in the P-side of the depletion region, as well as the negative terminal of the power supply and the positive ions in the N-side of the depletion region. The increased reverse bias voltage increases the width of the depletion layer, causing it to extend further into the P and N regions.

The widening of the depletion layer results in an increased width of the barrier between the P and N regions, which leads to a higher breakdown voltage and enables the Zener diode to maintain a relatively constant voltage across its terminals in the breakdown region. The specific breakdown voltage, known as the Zener voltage, is determined by the design and doping concentration of the diode.

So, in summary, as the reverse bias voltage applied to a Zener diode is increased, the thickness or width of the depletion layer also increases.