Question

Question 4.)

The Fermi Level Under Equilibrium Conditions is Constant. (True or False)

Question 6.) The Fermi level of a semiconductor doped with As (Group V) is : (choose one)

Above the valence band but below the middle of the bandgap.

Below the valence band edge.

Above the conduction band edge.

Above the middle of the bandgap and below the conduction band.

At the precise middle of the bandgap

15.) Choose all that applies for a semiconductor doped n-type:

It has more holes than electrons

Its fermi energy is located exactly at mid gap

Its conductivity depends on the amount of dopant added

It contains impurities

Its bandgap is smaller due to the doping

16.) Choose all that apply for an intrinsic semiconductor at room temperature

It has more holes than electrons

It has more electrons than holes

The Fermi level is located at midgap.

It has an equal number of electrons and holes

17.) Choose all that apply for a degenerate semiconductor:

It is excessively doped with donors or acceptors.

It must be n-type

It must be p-type

It's fermi energy is very close to the middle of the gap

20.) Diffusion currents can only exist in the presence of large electric fields (True or False)

Answer 1

4. Yes, at equilibrium the Fermi level is constant and does not change. It is constant because it is at equlibrium and there is no motion of electrons or holes that may cause a change in the Fermi level. So answer is True.

6. Group 5 elements are electron donors, hence the semiconductor becomes n-type. Since new electrons are added the Fermi level shifts upwards nearer to the conduction band edge, so the answer is Above the middle of the bandgap and below the conduction band.

15. for n-type doped semiconductors, impurities are added and the conductivity of the semiconductor depends on the amount of dopant added to the semiconductor, hence option 3 and 4 are correct. The band gap does not change due to doping.

16. For an intrinsic semiconductor, the total charge on it is zero, Hence the number of holes and electrons are equal, this implies that the Fermi level will be exactly midway, in the midgap. Hence option 3 and 4 are correct.