REFERENCES
- M. A. Wahab, SolidState Physics, Second Edition
- B.G. Yacobi, Semiconductor Materials: An Introduction to Basic Principles, Springer 2003 ISBN 0306473615, pp. 1–3
- http://www.gitam.edu/eresource/Engg_Phys/semester_2/semicon/int_ext.htm
- http://www.youtube.com/watch?v=HzwGOZ1QBXU