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Question -

In an intrinsic semiconductor the energy gap Egis1.2 eV. Its hole mobility is much smaller than electron mobility andindependent of temperature. What is the ratio between conductivity at 600K andthat at 300K? Assume that the temperature dependence of intrinsic carrierconcentration niisgiven by

where nisa constant.



Answer -

Energy gap of the given intrinsicsemiconductor, Eg =1.2 eV

Thetemperature dependence of the intrinsic carrier-concentration is written as:

Where,

kB =Boltzmann constant = 8.62 × 10−5 eV/K

T =Temperature

n0 =Constant

Initial temperature, T1 =300 K

Theintrinsic carrier-concentration at this temperature can be written as:

Final temperature, T2 =600 K

Theintrinsic carrier-concentration at this temperature can be written as:

 … (2)

The ratiobetween the conductivities at 600 K and at 300 K is equal to the ratio betweenthe respective intrinsic carrier-concentrations at these temperatures.

Therefore, the ratio between the conductivitiesis 1.09 × 105.

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