Answer to Question #283156 in Material Science Engineering for MD HUMAYAN KABIR

Question

Describe about quasi - Fermi level

Answer 1

Fermi level is the highest energy state occupied by electrons in a material at absolute zero temperature. As the temperature is increased, electrons start to exist in higher energy states too.

Loosely speaking, in a p type semiconductor, there is an increase in the Density of unfilled States.Thus, more electrons can be accommodated at lower energy states. In a n type semiconductor, the DOS is increased. Thus, electrons have to be accommodated at higher energy levels.

Fermi level is also defined as the work done to add an electron to the system. More positive (more holes) in a p type semiconductor, mean lesser work needs to be done. Hence a lower Fermi level.