The mechanism of flowing of electrons in semiconductor and concepts of hole

 The flow of electricity is happened due to the flow of electrons. But it is needed a medium of flowing a electrons. Those mediums are called the conductors. The conducting substances like metals reasonably flow electrons to flow the electricity. But there are some substances which doesn’t flow electrons. They are called the insulator. Today we are going to talk about the substances in between the insulators and the conductors. They are called the semiconductors. Germanium, Silicon, and Gallium are such an elements which can be fallen under the category of semiconductors. Today we will be talking about the mechanism of flow of the electrons and transversely, flow of electricity of these semiconductors. But before doing that we need to know about the energy band first. There are three types of energy bands like valance band, conduction band and forbidden energy band.

In case of the semiconductors, the valance band is almost electrically fulfilled. Whereas, the conduction band is almost empty and the energy differences between the two bands is low (about 1.1 eV).

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Germanium is mostly used semiconductor. There are four electrons at the valance shell of Germanium. So to fill the valance shell, the Germanium needs four more electrons. To do so, the Germanium make covalent bond with four other atoms of Germanium. And this way, Germanium form a crystal. At the 0K temperature, the covalent electrons of Germanium is cogently bounded. At this temperature, the covalent bond of Germanium is so strong. So, there is no free electrons at this stage and electricity doesn’t flow through. But when the temperature is increased, some of the covalent bond release electrons by deforming the bonds. Then some of the valance electrons enter the conduction band. When the valance electrons enter the conduction band, an empty place or a hole is generated at the valance bond. This hole works as the positive charge carrier. This positively charged hole attracts electrons from proximal atoms. Thus the flow of the electrons is generated. In this way, the semiconductor like Germanium works as a conductor.

Summary: The increase of temperature of semiconductor results in the increase of conductance.