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 ($Z=49$). These 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 N-type,Y is -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

Answer 1

The correct option is D X is N-type,Y is P-type and the junction is reverse biased

Arsenic has five valence electrons, so it is 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 the positive terminal of battery and P (i.e. Y) is connected to the negative terminal of battery. So P-N junction diode is reverse biased.