Semiconducting Devices Question 234
Question: A semiconductor X is made by doping a germanium crystal with arsenic (Z = 33). A second semiconductor Y is made by doping germanium with indium (Z = 49). The two are joined end to end and connected to a battery as shown. Which of the following statements is correct
[Orissa JEE 1998]
Options:
A) X is P-type, Y is N-type and the junction is forward biased
B) X is N-type, Y is P-type and the junction is forward biased
C) X is P-type, Y is N-type and the junction is reverse biased
D) X is N-type, Y is P-type and the junction is reverse biased
Show Answer
Answer:
Correct Answer: D
Solution:
Arsenic has five valence electrons, so it a donor impurity.
Hence X becomes N-type semiconductor.
Indium has only three outer electrons, so it is an acceptor impurity.
Hence Y becomes P-type semiconductor.
Also N (i.e.X) is connected to positive terminal of battery and P
(i.e.Y) is connected to negative terminal of battery so PN-junction is reverse biased.
