NEET Physics Question - Semiconductor Physics - Properties of Semiconductors

If the ratio of the concentration of electrons to 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 :

5/8

4/5

5/4

4/7

Solution:

The ratio of electron to hole currents is given by:

$\frac{I_n}{I_p} = \frac{7}{4}$ The ratio of electron to hole concentrations is:

$\frac{n}{p} = \frac{7}{5}$ Using the current formula

$I = q n v A$

$I = q n v A$ , the ratio of drift velocities (

$\frac{v_n}{v_p}$

$v ^{p} v ^{n}$ ) can be found as:

$\frac{I_{n}}{I_{p}} = \frac{n v_{n}}{p v_{p}}$ Substitute the given ratios: $\frac{7}{4} = \frac{\frac{7}{5} \cdot v_n}{v_p}$ Simplifying:

$\frac{v_{n}}{v_{p}} = \frac{5}{4}$

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Solution:

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