Semiconductors JEE Main previous year questions with solutions

5 solved JEE Main questions on Semiconductors, free to read — no sign-in needed. The full chapter has 205 questions; sign in to attempt the remaining 200 in the exam simulator.

1. Q1JEE Main 2026 (05 Apr, Shift 2)Diodes
   In a semiconductor p-n diode, the doping concentrations on p-side and n-side are $10^{15}\text{ atoms/cm}^3$ and $10^{18}\text{ atoms/cm}^3$, respectively. Which one of the following statements is true ?
   1. A.Widths of depletion region on either side of the interface are equal
   2. B.The depletion region width is more on p-side compared to that in n-side
   3. C.The depletion region width is more on n-side compared to that in p-side
   4. D.No depletion region forms because of unequal doping concentrations on p and n-sides
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   Answer: (B)

   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 $N_A = 10^{15} \text{ atoms/cm}^3$ and $N_D = 10^{18} \text{ atoms/cm}^3$. Substituting the values, we get: $10^{15} x_p = 10^{18} x_n$ $x_p = 10^3 x_n$ Since $x_p \gt x_n$, the depletion region penetrates more into the lightly doped side. Therefore, the depletion region width is more on the p-side compared to that in the n-side. Answer: The depletion region width is more on p-side compared to that in n-side
2. Q2JEE Main 2025 (04 Apr, Shift 2)Semiconductors
   Consider a n-type semiconductor in which $\mathrm{n}_{\mathrm{e}}$ and $\mathrm{n}_{\mathrm{h}}$ are number of electrons and holes, respectively. (A) Holes are minority carriers (B) The dopant is a pentavalent atom (C) $\mathrm{n}_{\mathrm{e}} \mathrm{n}_{\mathrm{h}} \neq \mathrm{n}_{\mathrm{i}}^2$ (where $n_i$ is number of electrons or holes in semiconductor when it is intrinsic form) (D) $\mathrm{n}_{\mathrm{e}} \mathrm{n}_{\mathrm{h}} \geq \mathrm{n}_{\mathrm{i}}^2$ (E) The holes are not generated due to the donors Choose the correct answer from the options given below :
   1. A.(A), (C), (D) only
   2. B.(A), (C), (E) only
   3. C.(A), (B), (E) only
   4. D.(A), (B), (C) only
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   Answer: (C)

   (A) n type semiconductor holes are minority carriers and $\mathrm{e}^{-}$are majority carriers (B) Dopant are pentavalent atom. (C) $\mathrm{n}_{\mathrm{e}} \cdot \mathrm{n}_{\mathrm{h}}=\mathrm{n}_{\mathrm{i}}^2$ for intrinsic semiconductor (E) In $n$ type semiconductor primary source of holes generation are thermal excitation.
3. Q3JEE Main 2024 (09 Apr, Shift 1)Energy Bands in Solids
   A light emitting diode (LED) is fabricated using GaAs semiconducting material whose band gap is $1.42 \mathrm{eV}$. The wavelength of light emitted from the LED is :
   1. A.$1400 \mathrm{~nm}$
   2. B.$650 \mathrm{~nm}$
   3. C.$875 \mathrm{~nm}$
   4. D.$1243 \mathrm{~nm}$
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   Answer: (C)

   $\lambda=\frac{1240}{1.42}=875 \mathrm{~nm}$ (Approx)
4. Q4JEE Main 2023 (29 Jan, Shift 1)Special purpose diodes
   Which of the following statement is not correct in the case of light emitting diodes? A. It is a heavily doped p-n junction. B. It emits light only when it is forward biased. C. It emits light only when it is reverse biased. D. The energy of the light emitted is equal to or slightly less than the energy gap of the semiconductor used. Choose the correct answer from the options given below :
   1. A.C and D
   2. B.A
   3. C.C
   4. D.B
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   Answer: (C)

   The structure of the LED has a high level of doping so that it can work on the principle of the interconversion of the light and electricity. It is in forward biased so that it can emit light spontaneously when connected as it reduces the efficiency of energy barrier. It will not emit light in reverse biased condition. The energy of radiation emitted by LED is not greater than the band gap of the semiconductor used.
5. Q5JEE Main 2021 (31 Aug, Shift 2)Rectifier
   Statement I : To get a steady DC output from the pulsating voltage received from a full wave rectifier we can connect a capacitor across the output parallel to the load ${R}_{L}.$ Statement II : To get a steady DC output from the pulsating voltage received from a full wave rectifier we can connect an inductor in series with ${R}_{L}.$ In the light of the above statements, choose the most appropriate answer from the options given below :
   1. A.Both Statement I and Statement II are false
   2. B.Both Statement I and Statement II are true
   3. C.Statement I is false but Statement II is true
   4. D.Statement I is true but Statement II is false
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   Answer: (B)

   We can improve the average, $DC$ output of the rectifier while at the same time reducing the $A.C.$ variation of the rectified output by using smoothing capacitors to filter the output waveform. Smoothing or reservoir capacitors connected in parallel with the load across the output of the full-wave bridge rectifier circuit increase the average $DC$ output level even higher as the capacitor acts like a storage device as shown below. Both Statement I and Statement II are true.