Q.Explain what is meant by an intrinsic semiconductor and describe, qualitatively, how electron-hole pairs are generated in it.

A chemically pure semiconductor crystal (silicon or germanium) with no added impurity. At $0$ K every valence electron is locked in a covalent bond and no free carriers exist; at any temperature above $0$ K, thermal vibration occasionally breaks a bond, freeing one electron and leaving one hole -- the vacancy that a neighbouring bond's electron can hop into, making the hole appear to migrate like a mobile positive charge. Because every broken bond releases exactly one of each, electrons and holes are always g …