#### Question

Define drift current, diffusion current and P-N junction. The electrical conductivity of a pure silicon at room temperature is 4×10^{-4 }mho/m . if the mobility of electron is 0.14m^{2 }/V-S and that of hole is 0.04m^{2 }/V-S. calculate the intrinsic

carrier density.

#### Solution

DRIFT CURRENT :-

Drift current is the electric current, or movement of charge carriers, which is due to the applied electric field, often stated as the electromotive force over a given distance.

DIFFUSION CURRENT:-

Diffusion current is a current in a semiconductor caused by the diffusion of charge carriers. This is the current which is due to the transport of charges occurring because of nonuniform concentration of charged particles in a semiconductor.

⦁ `P-N JUNCTION:-

A diode is a PN junction with p-type on one side and n-type on the other. When a positive voltage is applied to the p-type side , it shrinks and overcomes the depletion zone, causing the current flow from the p-type to the n-type side.

NUMERICAL:-

Given Data :- σ = 4×10^{-4}mho/m , μ_{e }= 0.14m^{2}/V-sec , μ_{h}= 0.04m2/V-S

Formula :- σ_{i} = n_{i} (μ_{e} + μ_{h} ).e

Calculations :- n_{i }= `(σi)/ ((μ_e + μ_h ).e)`

`=( 4×10^-4)/(1.6×10^(-19)(0.14+0.040)`

`n_i = 1.388 ×10^16/m^3`

Answer :- carrier concentration = 1.388 ×10^{16 }/m^{3 }