Question

If the ratio of the concentration of electrons and that of holes in a semiconductor is $7/5$ and the ratio of their currents is $7/4$ , then the ratio of their drift velocities is

• A. $4/7$
• B. $5/8$
• C. $4/5$
• D. $5/4$

Answer 1

Answer: (D)

Drift velocity $v_{\text{d}}=\frac{I}{\text{nAe}}$
$\frac{{\left(v_d\right)}_{electron}}{{\left(v_d\right)}_{hole}}=\left(\frac{I_e}{I_h}\right)\left(\frac{n_h}{n_e}\right)=\frac{7}{4}\times \frac{5}{7}=\frac{5}{4}$
Hence, the ratio of their drift velocities is $\frac{5}{4}$