Question

1. In the semiconductor materials fabrication process, Antimony material is injected into the silicon
wafer. Name the type of semiconductor product and explain the mechanism involved with the
schematic diagrams.

2. Describe the formation of the depletion region and the potential barrier of the PN junction (a)
without bias (b) forward bias and (c) reversed bias.

3.Explain on the cause and origin of the high reverse bias current after breakdown of a PN junction.

4.In bipolar Junction transistor,
(a) Why is the base layer is lightly doped and thin?
(b) Why is the base-collector junction connected in reverse biased?

5.Describe the operation of PNP bipolar junction transistor with the circuit diagram.

Answer 1

1. If Antimony material is injected into a sy silicon wafer it will form a n-type semicond- -uctor. Because, Antimony is a donor material which has five electrons in their valence shell.. In this type of doping this five electrons and three holes are added to the wo undoped material Since the sems conductor atoms have only four electrons and four holes in their valence shells, there is one entra electron for each impurity electron adoled. This electron will enters to the conduction band as a free electron. electron. semis conductor alors Impurity alom with fine electron 2. P-type n-type layer of the ions. - depletion region Longer of ave ions The movement of charge carriers across the junction leaves a layer on each side. This region is called depletion region. On each side of the junction equal numbers of impurity atoms are involved in