Question

(6) In the presence of an applied electric field, the bandgap of a semiconductor effectively

(   )

(A) Increases with increasing electric field, and decreases with decreasing temperature

(B) Decreases with increasing electric field, and increases with decreasing temperature

(C) Decreases with increasing electric field, and decreases with decreasing temperature

(D) Increases with increasing electric field, and increases with decreasing temperature

Answer 1

In each and every semiconductor we have a bandgap which is represented by Eg which is energy level between valance band and the conduction band based on the Eg we classify the type of material (i.e, conductor, insulator or semiconductor)

Now we have two conditions they are 1) applying an electric field

2) Increase in temperature

The band gaps of bilayer BP are smaller than that of monolayer BP, which means that the bandgaps of layered BP may decrease with the increasing layer number. All the bilayer BP materials are direct band gap semiconductors irrespective of the stacking orders. In addition, applying an external electric field on the bilayer BP, the band gap will increase (decrease) monotonously as the electric field increasing along positive direction of electric field (negative direction) for bilayer.

in the second case, The energy bandgap of semiconductors tends to decrease as the temperature is increased. This behaviour can be better understood if one considers that the interatomic spacing increases when the amplitude of the atomic vibrations increases due to the increased thermal energy. This effect is quantified by the linear expansion coefficient of a material. An increased interatomic spacing decreases the potential seen by the electrons in the material, which in turn reduces the size of the energy bandgap. Direct modulation of the interatomic distance, such as by applying high compressive (tensile) stress, also causes an increase (decrease) of the bandgap.

and are the fitting parameters.