Question

Which of the following are not examples of semiconductors?
A.Silicon
B.Germanium
C.Gold
D.Selenium

Answer 1

Hint: Semiconductors are the materials which have a conductivity between conductors (generally metals) and non-conductors or insulators. They generally work due to imbalance of electrons that carry negative charge.

Complete step by step answer:
In 1874, Karl Braun discovered and documented the first semiconductor diode effect. He observed that the current flows freely in only one direction and further in 1901, the very first semiconductor device known as “cat whiskers” was patented.
Generally, these are the materials which have a conductivity between conductors and insulators. Some of the examples of semiconductors are germanium, silicon etc. Now, let’s discuss the conduction band and valence band in semiconductors.
Basically, the energy band involving the energy levels of valence electrons is known as valence band. It is the highest occupied energy band. As compared to insulators, the band gap in semiconductors is smaller. It further allows the electrons in the valence band to jump into the conduction band whereas conduction band is the lowest unoccupied band that includes the energy levels of positive or negative charge carriers. In semiconductors, this band accepts the electrons from the valence band. The energy level diagram is as shown:

Now, among the given options Gold is not a semiconductor. It is a noble metal and is a good conductor of heat and electricity. The usage of gold is avoided in semiconductor technology because it acts like a deep level trap and recombination center.

Hence, option C is correct.

Note: Semiconductors are used in almost all the electronic devices. Their reliability, compactness, low cost makes them ideal to be used for various purposes in a wide range of components and devices. Moreover, transistors, diodes, photo sensors and much more devices are made up of semiconductors.