Semiconductors

Semiconductors

Semiconductors are devices which have electrical properties in between “conductor” and “insulator”. Examples of semiconductor materials are silicon (Si), gallium arsenide (GaAs), germanium (Ge) they have atoms which are closely arranged in a crystalline pattern known as crystal lattice because of which free electrons are less, and they flow only in special conditions.

The conductivity of semiconductors can be enhanced or changed by the addition of impurities as donors or acceptors to base material of silicon or germanium.  This leads to the production of free electrons or holes. The addition of donors or acceptors atoms into semiconductor atoms is known as doping. This leads to the formation of N-type and P-type semiconductors.

Silicon has four outermost valence electrons and by sharing with surrounding silicon atoms it forms complete eight electrons orbital which leads to the formation of a stable bond. In order to pass an electric current through it doping is done to create negative and positive terminals.

N-type semiconductors are created by doping with a pentavalent impurity (donors) and they show conductivity in the influence of electron movement. Doping here leads to positively charged donors, and negatively charged free electrons. Example of pentavalent impurity is antimony.

P-type semiconductors are created by doping with a trivalent impurity (acceptors) and they show conductivity in the influence of hole movement. Doping here leads to negatively charged acceptors and positively charged holes. Example of trivalent impurity is boron.

Semiconductors have led to the replacement of vacuum tubes, they form transistors, amplifiers, oscillators and lead to the formation of smart devices like solar cells, light-emitting diode (LED), rectifier diode, laser diode, etc.

 

 

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