Question

Problem #11) Please answer to the following questions: Semiconductor materials like Si and GaAs have electron-hole pairs as their intrinsic point defects. Using bonding as the starting point briefly explain why these materials don't have vacancies like metals or Schottky or Frenkel defects like ionic ceramics, as their primary intrinsic point defects.

Answer 1

Semiconductors like si and Gats Covalent bonded There are (i) All electrous are no free selectrons in pure Silicon to temperature coralent bonds break a few ralence increase ) the electrons are and released promoted into conduction band. Holes are formed that act as positive charges, to trinsic semi- forming conductors. (ii) Unlike Schottky and Frenkel coordination number defects where the and cations an is high anious are almost equal in size. eg. Nad kcl ete (111) Unlike Vacancies in metals where pas ticle is nrore to missing Lattice sites get a Vacancy. In metals displacement of metal atoms instead of excitation. Metals occur can't form electron- hole pair because of displacement owe 1 atom with other, on only vacancy. learing it