Question

Draw band structure diagrams for the following, highlighting on each diagram the valence band, conduction band and the band gap.

(a) Au,

(b) SiO2

(c) intrinsic Ge

(d) p-type Ge

(e) n-type Ge

On each of the band diagrams also indicate the probable location of the Fermi level for (c), (d) and (e) at a temperature of 0 K.

Answer 1

a) Here Au is a conductor hence the valence and the conduction Band will be overlaping so here electrons will be free, as shown Below

b) Basically SiO2 is an insulator hence its Valence and Conduction bands are separated by a huge energy gap called the band Gap. here electrons are bounded.

c) In case of Intrinsic semiconductors like Ge, the valence and conduction bands are separated but the band gap is low hence if we apply a certain ammount of energy electrons will flow from Valence to conduction band.

The fermi Energy level is situated in the middle of valence and conduction band.

d) in case of p-type Ge the fermi level will be closer to the valence band and there will be a accepter level above the fermi energy level

e) in case of n-type Ge the fermi level will be closer to the conduction band and there will be a doner level below the fermi energy level