In a semiconductor p -n diode, the doping concentrations on p -side and n -side are 10¹⁵ atoms /cm³ and 10¹⁸ atoms /cm³, respectively. Which one of the following statements is true? (a) Widths of depletion region on either side of the interface are equal (b) The depletion region width is more on p -side compared to that in n -side (c) The depletion region width is more on n -side compared to that in p -side (d) No depletion region forms because of unequal doping concentrations on p and n -sides

Answer: (b). Charge neutrality of the depletion layer: NA xp = ND xn. (xp)/(xn) = (ND)/(NA) = 10¹⁸10¹⁵ = 10³ The lightly doped p side has the wider depletion region. So the answer is (b).

In a semiconductor p -n diode, the doping concentrations on p -side… | JEE Main 2026 (5 Apr, Shift 2)

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P-N Junction Diode

In a semiconductor $p$ -n diode, the doping concentrations on $p$ -side and $n$ -side are $10^{15}$ atoms $/\text{cm}^{3}$ and $10^{18}$ atoms $/\text{cm}^{3}$ , respectively. Which one of the following statements is true?

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Answer: (b)

Charge neutrality of the depletion layer: $N_A x_p = N_D x_n$ .
$\dfrac{x_p}{x_n} = \dfrac{N_D}{N_A} = \dfrac{10^{18}}{10^{15}} = 10^{3}$
The lightly doped p side has the wider depletion region.
So the answer is (b).

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