Q. 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
A) $X$ is $P$-type, $Y$ is $N$-type and the junction is forward biased
B) $X$ is $P$-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
Explanation
(d) 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
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.