Engineering Physics

8.11 Direct and indirect band gap semiconductors

Based on the structure of energy bands, semiconductors are classified into: (i) Direct band gap semiconductors and (ii) Indirect band gap semiconductors.

This has been explained in the following way:

The electrons and holes present in a Semiconductor possess energies corresponding to allowed bands but none of them possesses energies correspond to energy gap. The energy of electrons and holes comprises both potential energy and kinetic energy. As they possess kinetic energy, they possess momentum. As shown in Figs. (8.13) and (8.14), graphs have been plotted between energy (E) versus momentum (ħK) or propagation vector (K) for direct band gap and indirect band gap semiconductors. In both the figures, ...