What is the effect of temperature on conductivity of semiconductor?
Electrical conductivity of semiconductor changes appreciably along with temperature changes. At absolute zero, this behaves as an insulator. At room temperature, due to thermal energy, several of covalent bonds of the semiconductor break. The breaking of bonds sets those electrons free that are engaged in the formation of these bonds. That results in few free electrons. Such electrons (e-) constitute a small current when potential is applied across the semiconductor crystal. It demonstrates the conductivity for intrinsic semiconductor raises with increase in temperature as specified by η = Aexp (-Eg / 2kt) where η is the carrier concentration, Eg is the band gap and T is the temperature and A is constant. When in extrinsic semiconductors, addition of small amount of impurities creates a large number of charge carriers. This number is too large which the conductivity of an extrinsic semiconductor is several times more than that of an intrinsic semiconductor at room temperature. At room temperature, in n - type semiconductor all the donors have donated their free electrons. The additional thermal energy only serves to rise the thermally produces carriers. This raises the minority carrier concentration. The temperature is reached while number of covalent bonds which are broken is large; therefore number of holes is around equal to number of electrons. Then extrinsic semiconductor behaves as intrinsic semiconductor.