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A semiconductor is known to have an elec...

A semiconductor is known to have an electron concentration of `5xx10^(12) cm^(-3)` and a hole concentration `8xx10^(13)cm^(-3) ` Is the semi-conductor n-type or p-type? What is the resistivity of the sample, if the electron mobility is `23,000 cm^(2) V^(-1)s^(-1)`? Take charge on electron, `e=1.6xx10^(-19) C`.

Text Solution

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Here,
`n_(e)=5xx10^(12)cm^(-3)=5xx10^(18)m^(-3)`,
`n_(h)=8xx10^(13)cm^(-3)=8xx10^(19)m^(-3)`,
`mu_(e)=23000cm^(2)V^(-1)s^(-1)=2.3m^(2)V^(-1)s^(-1)`,
`mu^(h)=100cm^(2) V^(-1)s^(-1)=0.01m^(2)V^(-1)s^(-1)`.
since the semiconductor has greater hole density, hence it is p-type
Now, `1/rho=e(n_(e)mu_(e)+n_(h)mu_(h)) =1.6xx10^(-19)[5xx10^(18)xx2.3+8xx10^(19)xx0.01]`
`1.6xx10^(-19)[1.15xx10^(19)+0.08xx10^(19)]`
`=1.968`
or `rho=1/1.968=0.508ohm-m`
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