Semiconductors and Electronic Devices Test - 3

As temperature increases electrons from the valence band go to the conduction band , so conductivity increases hence resistance decreases .

Silicon has a forbidden gap of 1.1  eV at 300 K temperature.
 

It is an N-type semiconductor because the density of electrons is more here.

• The electrons surrounding each atom in a semiconductor are part of a covalent bond . A covalent bond consists of two atoms "sharing " a single electron.
• Each atom forms 4 covalent bonds with the 4 surrounding atoms. Therefore, between each atom and its 4 surrounding atoms, 8 electrons are being shared.

• In the case ofinsulators , the energy gap is very large  while in the case of conductors energy gap is very short .
• This energy gap refers to the energy difference between the valence band and conduction band whereas, in semiconductors , this band gap value is in between that of conductors and insulators.

There are two types of semiconductors: p-type and n-type . Therefore both holes and electrons conduct current respectively.

Electrons in metal behave as gas.

The dielectric constant of a medium   K = ∈/∈₀  
where  ∈ is the permittivity of the medium.
For air, ∈= ∈₀ ​
⟹ K = 1

Given in question,

Mobilities of electrons μ_e ​= 0.36 ×m² V⁻¹ s⁻¹

Mobilities of holes μ_h ​= 0.17 ×m² V⁻¹ s⁻¹

densities of electron= densities of holes=2.5 ×10¹⁹ m⁻³

As we know, conductivity,
σ=1/p ​=e(μ_e ​n_e ​+μ_n ​n_n ​)
=1.6 ×10⁻¹⁹ [0.36 ×2.5 ×10¹⁹ +0.17 ×2.5 ×10¹⁹ )]
=2.12Sm⁻¹

So the electrical conductivity of germanium is 2.12Sm⁻¹

In semiconductors , the forbidden gap between the valence band and conduction band is very small. It has a forbidden gap of about 1 electron volt (eV).