Schottky Barrier vs. Avalanche Photodiodes: Key Differences

Photodiodes are semiconductor devices that convert light into electrical current, essential for a wide range of optical and communication applications. Among various types, the Schottky Barrier Photodiode (SBPD) and the Avalanche Photodiode (APD) are two important categories, each offering unique characteristics suited for specific uses. This page covers overview of their working principles, key differences and applications, helping to understand their selection for practical systems.

Schottky Barrier Photodiode

• A Schottky Barrier Photodiode uses a metal semiconductor junction to detect light instead of p-n junction.
• When light falls on the semiconductor, electron hole pairs are generated near the metal contact.
• These carriers are collected across the Schottky barrier producing a photocurrent.
• Advantages : Schottky diodes are known for very fast response and low capacitance
• Disadvantages : lower quantum efficiency compared to p-n photodiodes.

Schottky Barrier Photodiode

Avalanche Photodiode

• An Avalanche Photodiode is special highly reverse biased p-n junction photodiode.
• When photons generate carriers, they are accelerated by the strong electric field. This causes impact ionization and carrier multiplication.
• This leads to internal amplification of the photocurrent which makes them highly sensitive.
• Advantages : APDs are used where very low light detection is needed.
• Disadvantages : They are more complex and need high bias voltages.

Avalanche Photodiode

Difference between Schottky Barrier and Avalanche Photodiode types

Conclusion

SBPDs are preferred for high speed, low noise applications where internal gain is not needed, while APDs are ideal for ultra sensitive light detection with inherent gain at the cost of higher voltage requirements and more noise.