VTU Module - 2 | P-N Junctions

18EC33 | ELECTRONIC DEVICES | Module-2 VTU Notes

1. Forward and Reverse biased junctions- Qualitative description of Current flow at a junction, reverse bias, Reverse bias breakdown- Zener breakdown, avalanche breakdown, Rectifiers

Forward and reverse biased junctions are crucial to semiconductor physics, especially in diodes and transistors. These ideas are crucial for university electronics and electrical engineering students to comprehend semiconductor device behaviour.

a. Forward Biased Junction:

A diode in a forward-biased condition has a positive voltage on the p-side (anode) and a ground or lower voltage on the n-side. This voltage difference lowers the energy barrier between p-type and n-type semiconductor materials, making current passage across the diode easier. In this low "ON" state, the diode effectively conducts electricity and has low resistance. This feature is essential for rectifying AC into DC in power supply and other electronics.

b. Reverse Biased Junction:

In reverse-biased diodes, the p-side (anode) is linked to a negative voltage and the n-side (cathode) to a greater voltage. The diode's high resistance prevents current flow in this setup. This is the "OFF" or non-conducting state. The applied voltage raises the energy barrier between the p-type and n-type regions, making it difficult for charge carriers to pass the junction. To protect electronic circuits against reverse voltage or isolate sections, reverse biassing is often utilised.

Electronic circuit design and analysis require knowledge of forward and reverse biased junctions. Engineers and researchers can control current and voltage in semiconductor devices to create complex electronic systems for a variety of applications, from simple rectification in power supplies to complex integrated circuits in modern electronics. These ideas are essential to university electrical and electronics engineering education.

2. Optoelectronic Devices Photodiodes: Current and Voltage in an Illuminated Junction, Solar Cells, Photodetectors. Light Emitting Diode: Light Emitting materials

Modern technology relies on optoelectronic devices to convert light into electrical impulses and vice versa. Photodiodes are essential in telecommunications, medical imaging, and other applications.

Photodiodes are semiconductors with the photoelectric effect. Photodiodes generate a voltage proportional to light intensity when exposed to light. This makes them useful in sensing and detection.

Photodiodes' operation principles, material qualities, and applications are studied in university. Students study semiconductor materials, quantum mechanics, and electron-hole behaviour under illumination. They also learn about PIN, avalanche, and phototransistors, each designed for distinct performance needs.

Photodiodes are important for electrical engineering, physics, materials science, photonics, and optoelectronics students. This understanding underpins the construction of advanced sensors, optical communication systems, and imaging devices for healthcare, astronomy, and industrial automation.

In conclusion, photodiodes and other optoelectronic devices teach pupils about light and electricity. This knowledge gives them the skills to innovate in various businesses and develop optoelectronics technology.