Important semiconducting materials

Silicon, germanium, gallium arsenide and silicon carbide are the most important semiconducting materials.

Germanium is hard and dense. Its abundance in earth is only 0.0007%. It is available as germanium dioxide which is heated to high temperature in an hydrogen atmosphere to yield germanium. Crystal structure of germanium resembles with that of diamond with a forbidden energy gap around 0.67 eV. Its main application is in near infrared detection and in X-ray detectors.

Silicon is the most abundant element after oxygen with around 28%. Oxides of silicon in the form of sand or quartz are heated to obtain silicon. Purification is carried out by zone refining technique. Czochralski method is employed for growing silicon single crystals. Silicon assumes diamond crystal structure with forbidden energy gap around 1.1 eV.

Both silicon and germanium are indirect band semiconductors.

Gallium arsenide is a direct band gap semiconductor and hence is a suitable candidate for optoelectronic applications. Its bandgap is around 1.34 eV. It has larger electron mobility.

Silicon carbide is another semiconductor but not widely used.

Silicon remains as the first choice as a semiconductor since it is more abundant, non-toxic, ecofriendly, can operate upto 150 degree temperature, can easily grow a stable oxide, higher melting point and cheap.