Get premium membership and access questions with answers, video lessons as well as revision papers.

Discuss the Properties of PN Junction

Answers

- At the instant of pn-junction formation, the free electrons near the junction in the n region begin to diffuse across the junction into the p region where they combine with holes near the junction. The result is that n region loses free electrons as they diffuse into the junction. This creates a layer of positive charges (pentavalent ions) near the junction. As the electrons move across the junction, the p region loses holes as the electrons and holes combine. The result is that there is a layer of negative charges (trivalent ions) near the junction. These two layers of positive and negative charges form the depletion region (or depletion layer).
- The term depletion is due to the fact that near the junction, the region is depleted (i.e. emptied) of charge carries (free electrons and holes) due to diffusion across the junction. It may be noted that depletion layer is formed very quickly and is very thin compared to the n region and the p region. For clarity, the width of the depletion layer is shown exaggerated.

- Once pn junction is formed and depletion layer created, the diffusion of free electrons stops. In other words, the depletion region acts as a barrier to the further movement of free electrons across the junction. The positive and negative charges set up an electric field. This is shown by a black arrow in Fig. 2.19 (i). The electric field is a barrier to the free electrons in the n-region. There exists a potential difference across the depletion layer and is called barrier potential (V₀). The barrier potential of a pn junction depends upon several factors including the type of semiconductor material, the amount of doping and temperature. The typical barrier potential is approximately: For silicon, V₀ = 0.7 V ; For germanium, V₀ = 0.3 V
Fig. 2.20 shows the potential (V₀) distribution curve.

Wilfykil answered the question on August 14, 2019 at 05:33

Next: What is a PN Junction and how is it formed?
Previous: Explain the Current Flow in a Forward Biased pn Junction

View More Electronics Questions and Answers | Return to Questions Index

Learn High School English on YouTube

Discuss the Properties of PN Junction

Answers

Related Questions