Variation of Fermi Energy Level with Temperature and Impurity Concentration in 'p' - Type Semiconductor

VARIATION OF FERMI ENERGY LEVEL WITH TEMPERATURE AND IMPURITY CONCENTRATION IN P-TYPE SEMICONDUCTOR

When the temperature is increased, some of the electrons in the valence band will go to acceptor energy levels by breaking up the covalent bonds and hence the Fermi level is shifted in upward direction for doping level of N_d = 10²¹ atoms/m³ as shown in Fig. 2.20.

From the Fig. 2.20 it can be seen that for the same temperature, if the impurity atoms (i.e.,) doping level is increased say N_a = 10²⁴ atoms/m³, the hole concentration increases and hence the Fermi level decreases.

Therefore at low temperature the Fermi energy level may be increased upto the level of intrinsic energy level (E_i)

Results

• Density of holes (n_h) in the valence band is proportional to the square root of the acceptor energy level.

• When temperature is increased the Fermi energy level increases, at low temperature it increases upto intrinsic Fermi level (E_i).