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Physics Question on Semiconductor electronics: materials, devices and simple circuits

The conductivity of semiconductor increases with increase in temperature because

A

both number density of charge carriers and relaxation time increase

B

number density of charge carriers increases

C

number density of current carriers increases, relaxation time decreases but effect of decrease in relaxation time is much less than increase in number density

D

relaxation time increases

Answer

number density of current carriers increases, relaxation time decreases but effect of decrease in relaxation time is much less than increase in number density

Explanation

Solution

As temperature increases the number density of charge carries increases according to the equation n=CT32.exp(−E2kT).n=CT^{\frac{3}{2}}. exp\left(-\frac{E}{2}kT\right). Thus as temperature increases, the number density of charge carries increase resulting in conductivity of semiconductors.