Question

How are metals used as semiconductors refined? What is the principle of the method used?

Answer 1

Zone refining method.

• Metal used as semiconductor is refined by Zone refining method.

• This method is based on the principle that the impurities are more soluble in the melt than in the solid state of the metal.

• In this method a mobile heater surrounding the rod of impure metal is fixed at its one end. The molten zone moves along with the heater which is moved forward. As the heater moves forward, the pure metal crystallizes out of the melt left behind and the impurities pass on into the adjacent new molten zone created by movement of heaters. The process is repeated several times and the heater is moved in the same direction again and again. Impurities get concentrated at one end. This end is cut off.