Distinguish between intrinsic and extrinsic semi conductors and give TWO examples of each. – NABTEB QUESTION

If conduction in material results only from the electron movement from valence to conduction band, it is called an intrinsic semiconductor. While semiconductor materials containing different types of impurities are combine to produce the many useful devices presently on the scene. The process of adding impurity to a semiconductor is called doping, and the doped semiconductor is referred to as extrinsic semi conduction.
E.g.

(i) Intrinsic – Pure silicon, Germinium etc.
(ii) Extrinsic: – Gallium Arsenide, (gasa), Lead Tellurium (PbTe) etc.