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  • Stuck here, help me understand: In the ratio of the concentration of electrons that of holes in a semiconductor is 7/5 and the ratio of currents is 7/4 then what is the ratio of their drift velocities?

In the ratio of the concentration of electrons that of holes in a semiconductor is 7/5 and the ratio of currents is 7/4 then what is the ratio of their drift velocities?

  • Option 1)

    4/7

  • Option 2)

    5/8

  • Option 3)

    4/5

  • Option 4)

    5/4

 

Answers (1)

best_answer

As we have learnt,

 

Electrical Conductivity (σ) -

\sigma =e \left (n_{e}\mu _{e}+n_{h}\mu _{h} \right )
 

- wherein

n_{e}= electron \: density

n_{h}= hole \: density

\mu _{e}= mobility \: of \: electron

\mu _{h}= mobility \: of \: holes

 

 \frac{n_e}{n_h} = \frac{7}{5}, \; \frac{I_e}{I_h} = \frac{7}{4}

I = nv_\alpha eA

\\\frac{I_e}{I_h} = \frac{n_ev_{d,e}}{n_h v_{d,h}} \Rightarrow \frac{v_{d,e}}{v_{d,h}} = \frac{I_e}{I_h}\cdot\frac{n_h}{n_e} \\\frac{v_{d,e}}{v_{d,h}} = \frac{7}{4}\times \frac{5}{7} = \frac{5}{4}

 


Option 1)

4/7

Option 2)

5/8

Option 3)

4/5

Option 4)

5/4

Posted by

Aadil

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