14. Answer the following (True or False problem) a) For metals, empty states are

Question

14. Answer the following (True or False problem) a) For metals, empty states are always available right above the filled electron states: True or False? For n-type semiconductors, the electron concentrations (the number of electro centimeters) can be controlled by adjusting the concentrations of donors: True If the concentration of phosphor atoms (donors) in a semicond then the density of electrons of the semiconductor is about 10% of the donor concentration, ie., ~1 × 1014 [1/cm) at room temperature: True or False? For an intrinsic semiconductor, the number of electrons and the number of holes are the same: True or False? b) ns per cubic c) uctor is 1 x 1015 [1/cm d) e) For an intrinsic semiconductor, the hole concentration decreases with increasing temperature: True or False?

Explanation / Answer

a)TRUE----Electrons fills states on the electrode from lower energy level to higher energy level untill all electrons gets accomodated.So any materials has more number of states than that is required for the electrons to be standard energy level.Therefore empty states are always available right above the filled electron states.

b)TRUE-----In n-type semiconductor,it posses 5 valence electrons and each atom covantly tries to bond with five lattice atoms.Conduction process is dominated by donors. So the electron concentration can be controlled by adjusting the concentration of donors.

c)FALSE--- The donor density is thousand times the elcetron density or we can say that the electro density is 0.001 times the donor density.

So,if the donor density is 10^15(1/cm^3) then electron density= 0.001*10^15(1/cm^3)

=10^12(1/cm^3)

d)TRUE-- At absolute zero temperature,intrinsic semiconductor behaves like a perfect insulator.

In case of intrinsic semiconductor,the number of holes present in valance band is equal to number of electrons present in conduction band.So the given statement is true.

e)FALSE----As the temperature is increased,free electrons and holes gets generated in case of intrinsic semiconductor.Means the hole concentration increases with increasing temperature.So the abov statement is FALSE.

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