This document discusses photodiodes and is presented by a group of six students. It defines a photodiode as a PN-junction diode that produces electric current from light energy. Photodiodes are made up of P-type and N-type semiconductor layers and work in reverse bias conditions to generate a current when illuminated with light. They can be used for applications like photodetection, optical communication, and counting. The document also describes the construction, working principle, V-I characteristics, dark current, and main types of photodiodes.

1. Presentation of PHYSICS
Photo diode

2. Group members
• Zain ul Abidien(Leader) 439
• Asad Ali 481
• Junaid Babar 407
• Zain ul Abidien 406
• Faizan Arif 443
• Shamon 463

3. What is Photodiode?
A photodiode is a PN-junction
diode that consumes light
energy to produce an electric
current. They are also called
a photo-detector, a light
detector, and a photo-sensor.
Photodiodes are designed to
work in reverse bias
condition. Typical photodiode
materials are Silicon,
Germanium and Indium
gallium arsenide.

4. Construction
The photodiode is made up of two layers of P-type and N-
type semiconductor. In this, the P-type material is formed
from diffusion of the lightly doped P-type substrate.Thus,
the layer of P+ ions is formed due to the diffusion process.
And N-type epitaxial layer is grown on N-type substrate.

5. Working of Photodiode
• When the Photodiode is illuminated with light, with Energy greater than
Energy gop of the Semi-Conductor than electron hole puir are generated
due to the absorption of photons these charge Carriers. Contribute to the
reverse current.

6. Uses of Photodiode
• In photodetection for optical signals.
• In demodulation for optical signals.
• In optical communication equipment.
• In counting machine.

7. V-I Characteristics
• I1,I2,I3 and I4 is not a current ,It is intensity of light.
• On increasing intensity , reverse current also
increase.

8. Dark Current
When the photodiode is reverse biased with a voltage less than its
breakdown voltage and no light is incident on its junction the
reverse current is extremely small .This current is called dark
current .

9. Types of photodiode
• PIN photodiode.
• P-N photodiode.
• Avalanch photodiode.