Photodiodes

Photodiodes are used in an array of every day electronic devices such as camera's, smoke detectors, burglar alarms, safety equipment, medical applications, CD players and surveying instruments to name a few.

What is a photodiode?

They are used as light sensors or detectors. When light reaches a photodiode, this is converted to electrical energy in the form of an electric current. The photocurrent that is produced is proportional to the amount of light. Photodiodes can also be known as photosensors, photodetectors and light detectors.

Photonic applications use the photon in the same way as electronic applications use the electron. There is usually a small amount of electric current that flows through these photosensitive devices even when no light (photons) are entering it. This is known as dark current.

What are the different types?

The PN photodiode was the first to be developed, it is not so widely used these days due to their relatively low performance compared to newer technologies.

The PIN photodiode has a wider surface area and allows for more light photons to be collected, as well as having a lower capacitance. It is the most widely used diode today.

Avalanche photodiodes are used in areas where there is low light, it operates under a high reverse bias condition. The higher the reverse voltage, the higher the gain.

Schottky photodiode is based on the schottky diode, or shottky barrier diode. It provides additional functions over others, particularly with regards to high speed and long wavelength detection.