Case Study: Read the following paragraph and answer the questions.
Light emitting diode is a photoelectric device which converts electrical energy into light energy. It is a heavily doped p-n junction diode which under forward biased emits spontaneous radiation. The general shape of the I - V characteristics of an LED is similar to that of a normal p-n junction diode, as shown. The barrier potentials are much higher and slightly different for each colour.

(i) The I - V characteristic of an LED is
(ii) Draw the schematic symbol of light emitting diode(LED)

(iii) An LED is constructed from a p-n junction based on a certain Ga-As-P semiconducting material whose energy gap is 1.9 eV. Identify the colour of the emitted light.
OR
(iii) Why are LEDs made of compound semiconductor and not of elemental semiconductors?

Question

Case Study: Read the following paragraph and answer the questions.
Light emitting diode is a photoelectric device which converts electrical energy into light energy. It is a heavily doped p-n junction diode which under forward biased emits spontaneous radiation. The general shape of the I - V characteristics of an LED is similar to that of a normal p-n junction diode, as shown. The barrier potentials are much higher and slightly different for each colour.

(i) The I - V characteristic of an LED is
(ii) Draw the schematic symbol of light emitting diode(LED)

(iii) An LED is constructed from a p-n junction based on a certain Ga-As-P semiconducting material whose energy gap is 1.9 eV. Identify the colour of the emitted light.
OR
(iii) Why are LEDs made of compound semiconductor and not of elemental semiconductors?

Accepted Answer

(i) (b) The I - V characteristics of an LED is similar to that of a Si junction diode. But the threshold voltages are much higher and slightly different for each colour.

(ii)

(iii) $As E_{g} = \frac{hc}{λ} ∴ λ = \frac{hc}{Eg}$

OR

(iii) LEDs are made up of compound semiconductors and not by the elemental conductor because the band gap in the elemental conductor has a value that can detect the light of a wavelength which lies in the infrared (IR) region.

Best Courses for You

Detailed Solution

courses

Get Expert Academic Guidance – Connect with a Counselor Today!

best study material, now at your finger tips!

download the app

Download the App