Engineering Physics

8.3 Electrical conductivity of a semiconductor

In a semiconductor, the conduction band electrons and valence band holes will participate in electrical conduction. To obtain an expression for electrical conductivity, we consider a rectangular bar of intrinsic semiconductor connected to a battery as shown in Fig. 8.3. Then, electric field exists along X-direction. This field accelerates the free (or conduction band) electrons along negative X-direction and holes along X- direction. So, the velocity of electrons along negative X-direction increases and attains some constant resultant velocity. This constant velocity is called drift velocity, represented as v_d. This drift velocity is superimposed on their random thermal motion. The total electrical ...