Question: 16 -

The intrinsic carrier density at 300K is 1.5 * 10¹⁰/cm³ , in silicon for n-type silicon doped to 2.25*10^¹⁵ atoms/cm³ , the equilibrium electron and hole densities are

n = 1.5 * 10¹⁰/cm³, p=1.5*10¹⁰/cm³

n = 1.5 * 10¹⁰/cm³, p=2.25*10¹⁵/cm³

n = 1.5 * 10¹⁵/cm³, p=1.5*10¹⁰/cm³

n = 2.25 * 10¹⁵/cm³, p=1.0*10⁵/cm³

Answer:

n = 2.25 * 10¹⁵/cm³, p=1.0*10⁵/cm³

Solution not available.

Question: 17 -

According to the Einstein relation , for any semiconductor the ratio of diffusion constant to mobility of carriers:

Is a universal constant

Varies with life time of the semiconductor

Depends upon the temperature of the semiconductor

Depends upon the type of the semiconductor

Answer:

Depends upon the temperature of the semiconductor

Solution not available.

Question: 18 -

Direct band gap semi conductors

Exhibit short carrier life time and they are used for fabricating BJT's

Exhibit long carrier life time and they are used for fabricating lasers

Exhibit short carrier life time and they are used for fabricating lasers

Exhibit long carrier life time and they are used for fabricating BJT's

Answer:

Exhibit short carrier life time and they are used for fabricating lasers

Solution not available.

Question: 19 -

A silicon Sample is uniformly doped with 10¹⁶phosphorous atoms / cm³ and 2 * 10¹⁶ boron atoms / cm³ If all the dopants are fully ionized , the material is

p-type with carrier concentration of 2*10¹⁶/cm³

n-type with carrier concentration of 10¹⁶/cm³

p-type with carrier concentration of 10¹⁶/cm³

n-type with carrier concentration of 2*10¹⁶/cm³

Answer:

p-type with carrier concentration of 10¹⁶/cm³

Solution not available.

Question: 20 -

In a p-type semiconductor , the fermi level lies 0.39 ev above the valence band . Determine the new position of the fermi level if the concentration of acceptor atoms is tripled . Assume KT = 26 mV

0.36 eV

0.40 eV

No change

0.44 eV

Answer:

0.36 eV

Solution not available.