Power System Engg

                                      Semiconductor

The term “semiconducting” was used for the first time by Alessandro Volta in 1782.Michael Faraday was the first person to observe a semiconductor effect in 1833. The article “semiconductor technology” is about how doping works in n-type and p-type semiconductor.

 (https://www.halbleiter.org/en/fundamentals/conductors-insulators-semiconductors/ and https://www.halbleiter.org/en/fundamentals/doping/ ) .

Doping is defined as the introduction of small amount of impurities into a pure crystal to increase their conductivity. Hence conductivity of silicon and germanium can be increase by doping it with some other elements. Doping plays a very important role in both N-type and P-type semiconductor. Si and Ge belongs to group 14 of the periodic table and have four valence electrons. Hence in their crystal Si and Ge atom can form four covalent bond with its neighbors. Now in case of N -type semiconductor doping can be done by addition of some of the atom of group fifteen having five valence shell electrons. Hence four of the five electrons of group 14 are shared by electron of group 15 and form covalent bond. One electron remains free and carry negative charge so due to this reason, it is called N-type semiconductor.

                                                   [pic 1]

                                                             (Doping in N-type semiconductor)

Same can be done in P-type semiconductor, but in this case doping can be done by addition of some of the element of group 13 having 3 valence shell electrons which then form three covalent bond with electron of group 14. Since the fourth electron is missing and then electron from neighbor atom can come and fill that hole. so, another hole will be created which carry positive charge. Due to this positive hole in the crystal, this semiconductor is called P-type semiconductor.