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In a p-n junction, the thickness of depl...

In a p-n junction, the thickness of depletion region is `2xx10^(-7)m` and potential barrier across the junction is 0.20 V
(a) What will be the intensity of electric field in this region ?
(b) if an electron, from n-side approaches the p-n junction with speed `5xx10^(5) m//s`. then with what speed it will enter the p-side ?

Text Solution

Verified by Experts

(a) Thickness of depletion region `=2xx10^(-7)m`
Electric field intensity `E=V/d=0.20/(2xx10^(-7))=1xx10^(6) ms^(-1)`
(b) Suppose an electron enters the depletion layer with speed `v_1` and p-region with speed `v_(2)`

By energy conservation
`1/2 mv_(1)^(2)=eV+1/2 mv_(2)^(2)`
`rArr mv_(1)^(2)=2eV+mv_(2)^(2) " " v_(1) =5xx10^(5) ms^(-1)`
`rArr mv_(2)^(2) =mv_(1)^(2)-2eV " " m=9.1xx10^(-31)kg`
`e=1.6xx10^(-19)c`
`rArr v_(2)^(2) =(mv_(1)^(2)-2eV)/m " " V=0.20 V`
`rArr v_(2) =sqrt(mv_(1)^(2)-2eV)/m)`
`rArr v_(2)=sqrt((9.1xx25xx10^(-21)-64xx10^(-21))/(9.1xx10^(-31)))=13.40 xx10^(5) ms^(-1)`
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