JEE Main20265 April 2026Evening ShiftPhysicsSemiconductorsActual
In a semiconductor p-n diode, the doping concentrations on p-side and n-side are 10¹⁵ atoms/cm ^3 and 10¹⁸ atoms/cm ^3 , respectively. Which one of the following statements is true ?
Options
- AWidths of depletion region on either side of the interface are equal
- BThe depletion region width is more on p-side compared to that in n-side
- CThe depletion region width is more on n-side compared to that in p-side
- DNo depletion region forms because of unequal doping concentrations on p and n-sides
Correct answer
B. The depletion region width is more on p-side compared to that in n-side
Step-by-step solution
In a p-n junction diode, the total charge on both sides of the depletion region must be equal to maintain charge neutrality. Let x_p and x_n be the widths of the depletion region on the p-side and n-side, respectively. Let N_A and N_D be the doping concentrations on the p-side and n-side. The charge neutrality condition is given by: N_A x_p = N_D x_n Given N_A = 10¹⁵ atoms/cm ^3 and N_D = 10¹⁸ atoms/cm ^3 . Substituting the values, we get: 10¹⁵ x_p = 10¹⁸ x_n x_p = 10^3 x_n Since x_p > x_n , the depletion region pe