Semiconductor diodes

  P-N Junction 

We have already discussed about the p-type and n-type semiconductors in the previous tutorial. To read about p-type and n-type semiconductors click on this links (p-type semiconductor, n-type semiconductor).

The n-type semiconductor is formed by adding pentavalent impurities to the intrinsic semiconductor while p-type semiconductor is formed by adding trivalent impurities to the intrinsic semiconductor. 

Also, in n-type semiconductors electrons are the majority carriers while holes are the minority carriers. On the other hand, in p-type semiconductors holes are the majority carriers while electrons are the minority carriers. The p-type and n-type semiconductors are not used separately for practical purpose because the overall charge of p-type and n-type semiconductors is electrically neutral.  However, when p-type and n-type semiconductor materials are joined they behave differently.

Remember that although n-type semiconductor has large number of free electrons, but these free electrons are provided by the pentavalent atoms that are electrically neutral. Thus, the n-type semiconductor is electrically neutral. Similarly, in p-type semiconductor holes are provided by the trivalent atoms that are electrically neutral. Therefore, overall charge of p-type semiconductor is also neutral.

Formation of p-n junction

Generally junction refers to a point where two or more things are joined. For example, when one or more railway tracks are joined a railway junction is formed. The region where the tracks meet or joined is called railway junction.

In the similar way, when an n-type semiconductor is joined with the p-type semiconductor, a p-n junction is formed. The region where the p-type and n-type semiconductors are joined is called p-n junction. It is also defined as the boundary between p-type and n-type semiconductor. This p-n junction forms a most popular semiconductor device known as diode. 

P-n junction is also a fundamental building block of many other semiconductor electronic devices such as transistors, solar cells, light emitting diodes, and integrated circuits. The credit of discovery of the p-n junction goes to American physicist Russel Ohi of Bell Laboratories.

Semiconductor devices are the fundamental building blocks of all the electronic devices such as computers, control systems, ATM (Automated Teller Machine), mobile phones, amplifiers, etc. Diodes are the simplest form of all the semiconductor devices. The various applications of diodes include computers, power supplies, television, radios and so on.

Before the invention of semiconductor diode there was vacuum tubes which are large in size, takes more power, costly, and noisy. This problem was solved with invention of semiconductor diode. Semiconductor diodes are small in size, low cost and consume less power.