Smart vehicles, intelligent machines, and advanced devices are increasingly becoming autonomous. The roles of optical communication and distance measurement are significant as the environment is perceived accurately, and accordingly, there is a reaction. APD or avalanche photodiode is the device that can render benefits in such applications and several other cases. When an organization incorporates communication or measurement solutions handling low light levels, APD can cater to the challenges.

What are APDs?

Avalanche photodiodes are highly delicate semiconductor devices that can alter optical signals into electrical signals. Furthermore, the diodes also consist of an internal gain mechanism. Thanks to the presence of a gain mechanism, the lowest optical signal strengths, and independent photons can be detected. The terminology refers to the internal gain mechanism, which is also known as the avalanche breakdown.

Benefits of avalanche photodiodes

The use of APD devices is widespread in various industrial sectors. It is because of their wide range of benefits.

  • APDs have high performance
  • Avalanche photodiode devices can easily identify low-intensity light
  • The sensitivity range of APDs is high
  • The response time is significantly quicker
  • A huge number of charge carrier pairs are generated via a single photon of APD

The working mechanism of Avalanche Photodiode

The breakdown happens primarily when the photodiode is under the maximum reverse voltage. The voltage heightens the electric field beyond the depleted layer. The accidental light enters the p+ area, and then it gets drawn within the highly noncompliant p area. The charge carriers are subjected to motion. It includes the drifting of the saturation velocity to the pn+ area every time a significantly high electric field survives. When the velocity is at the highest level, the charge carriers will clash with other existing atoms and create new electron-hole pairs. The creation of pairs from charge carriers will give rise to the prominent photocurrent.

Independent driving with APDs

Road traffic has become safer, more autonomous, and more efficient. When driving, the advanced driver assistance application evaluates multiple aspects like speed limits, the distance between vehicles, obstacles on the road, and so on. The use of speed measurement and optical distance has paved the way for self-driving cars. The advanced technology enables constant monitoring of the surrounding from within the car and ensures safe driving. The applications installed in such automated driving or self-driving cars are tiny detector modules. The compact modules depend on the accurate avalanche photodiode.

Applications of APDs

Avalanche photodiodes enable fast and accurate measurements, particularly when low signals are there in distance measurement and optical communication systems. APDs are employed in multiple industrial applications.

  • Speed gun
  • Laser microscopy
  • Barcode reader
  • PET scanner
  • Laser scanner
  • Optical fiber communication receivers
  • Antenna analyzer bridge
  • Laser rangefinders


When optical fiber communication systems or any other applications are in use, avalanche photodiode are used to detect weak or low signals. The circuits used must be optimized adequately to acquire the perfect signal-to-noise ratio. To ensure the signals are noticed, the quantum efficiency must be at a higher level and the maximum value.