Question
A semiconductor has equal electron and hole concentration of 2 x 108/m3. On doping with a certain impurity, the hole concentration increases to 4 x 1010/m3.
(i) What type of semiconductor is obtained on doping?
(ii) Calculate the new electron concentration of the semiconductor.
(iii) How does the energy gap vary with doping?
Solution
Given,
Intrinsic concentration, ni = 2 x 108/m3
After doping,
Hole concentration, nh = 4 x 1010/m3
i) Since there is an increase in hole current, the semiconductor formed is p-type.
ii) We know that,
ni2 = ne.nh
=
ne = 106 m-3 is the new electronic concentration.
iii) Energy gap decreases with doping because an acceptor levels gets created between valence band and conduction band.
Intrinsic concentration, ni = 2 x 108/m3
After doping,
Hole concentration, nh = 4 x 1010/m3
i) Since there is an increase in hole current, the semiconductor formed is p-type.
ii) We know that,
ni2 = ne.nh
=
ne = 106 m-3 is the new electronic concentration.
iii) Energy gap decreases with doping because an acceptor levels gets created between valence band and conduction band.
