What is the minimum band-gap of the LED diode?
Show Hint
- 1.5 eV
- 1.7 eV
- 1.8 eV
- 0.8 eV
The Correct Option is C
Solution and Explanation
- Above 3 eV: Emission shifts to UV region.
So, 1.8 eV is the minimum band-gap needed to emit visible light.
Top Questions on Semiconductors
- Two statements are given, one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer from the codes (A), (B), (C), and (D) as given below.
Assertion (A): The impurities in p-type Si are not pentavalent atoms.
Reason (R): The hole density in the valence band in a p-type semiconductor is almost equal to the acceptor density.
- CBSE CLASS XII - 2025
- Physics
- Semiconductors
Extrinsic semiconductors are made by doping pure or intrinsic semiconductors with suitable impurity. There are two types of dopants used in doping, Si or Ge, and using them p-type and n-type semiconductors can be obtained. A p-n junction is the basic building block of many semiconductor devices. Two important processes occur during the formation of a p-n junction: diffusion and drift. When such a junction is formed, a ’depletion layer’ is created consisting of immobile ion-cores. This is responsible for a junction potential barrier. The width of a depletion layer and the height of potential barrier changes when a junction is forward-biased or reverse-biased. A semiconductor diode is basically a p-n junction with metallic contacts provided at the ends for application of an external voltage. Using diodes, alternating voltages can be rectified.
- CBSE CLASS XII - 2025
- Physics
- Semiconductors
- When a p-n junction diode is forward biased, the:
- CBSE CLASS XII - 2025
- Physics
- Semiconductors
- A p-type Si semiconductor is made by doping an average of one dopant atom per \( 5 \times 10^7 \) silicon atoms. If the number density of silicon atoms in the specimen is \( 5 \times 10^{28} \, \text{atoms m}^{-3} \), find the number of holes created per cubic centimeter in the specimen due to doping. Also give one example of such dopants.
- CBSE CLASS XII - 2025
- Physics
- Semiconductors
- In the given circuit, if \( A = 0 \), \( B = 1 \), and \( C = 1 \) are inputs, then the values of \( y_1 \) and \( y_2 \) are respectively
- AP EAPCET - 2025
- Physics
- Semiconductors
Questions Asked in COMEDK UGET exam
A solid cylinder of mass 2 kg and radius 0.2 m is rotating about its own axis without friction with angular velocity 5 rad/s. A particle of mass 1 kg moving with a velocity of 5 m/s strikes the cylinder and sticks to it as shown in figure.
The angular velocity of the system after the particle sticks to it will be:- COMEDK UGET - 2024
- The Angular Momentum
- A transformer which steps down 330 V to 33 V is to operate a device having impedance 110 $\Omega$. The current drawn by the primary coil of the transformer is:
- COMEDK UGET - 2024
- Transformers
- In the Young's double slit experiment, the 2nd bright fringe for red light coincides with the 3rd bright fringe for violet light. Then the value of 'n' is: (Given: wavelength of red light = 6300 $\text{Å}$ and wavelength of violet light = 4200 $\text{Å}$)
- COMEDK UGET - 2024
- Youngs double slit experiment
- If 216 drops of the same size are charged at 200 V each and they combine to form a bigger drop, the potential of the bigger drop will be
- COMEDK UGET - 2024
- Electrostatics
- The domain of the function $ y = \frac{1}{\log_{10}(3 - x)} + \sqrt{x + 7} $ is:
- COMEDK UGET - 2024
- Functions