... gap in an intrinsic semiconductor. In addition, the Fermi energy can be thought of as the average energy of mobile carriers in a semiconductor mate-rial. In an n-type semiconductor, there ... formed by diffusing into an n-type semiconductor a p-type impurity atom, or vice versa. Because the p-type semiconductor has many free holes and the n-type semiconductor has many free electrons, ... Intrinsic, (b) N-type, and (c ) P-type Semiconductors. 10.2.3 Current density and mobility Two mechanisms account for the movement of carriers in a semiconductor ma-terial: drift and diffusion....