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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 0.14m2 /V-S and that of hole is 0.04m2 /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 = 4×10-4mho/m , μe = 0.14m2/V-sec , μh= 0.04m2/V-S
Formula :- σi = ni (μe + μh ).e
Calculations :- ni = `(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 ×1016 /m3
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