APDs Avalanche Photodiodes

An Avalanche Photodiode (APD) is a photodetector that provides a built-in first stage of gain via avalanche multiplication. Provision of this internal signal gain is what differentiates an APD from a PIN photodiode.

An APD provides higher sensitivity than a standard photodiode. APDs are ideal for extreme low-level light detection and photon counting. Available as Silicon or InGaAs photodiodes, these devices provide detectivity from 400 nm - 1100 nm. Multiple configurations are available to provide a wide range of sensitivity and speed options, with additional pre-amplifier and filter options available to tailor the device to meet specific requirements.

The use of avalanche photodiodes instead of PIN photodetectors will result in improved sensitivity in many applications. In general, they are useful in applications where the noise of the amplifier is high — i.e. much higher than the noise in the PIN photodetector. Thus, although an APD is always noisier than the equivalent PIN, improved signal-to-noise can be achieved in the system for APD gains up to the point where the noise of the APD is comparable to that of the amplifier. In very low bandwidth systems, the noise of the amplifier is likely to be very low, in which case, an avalanche photodiode may not be the best choice.

Excelitas offer products including:

  • High-volume, cost effective silicon APDs for Range Finding and Laser Meter applications
  • Large area, UV-enhanced versions for Molecular Imaging (PET).
  • Long wavelength enhanced versions for Analytical Applications.
  • Multi element and quadrant APDs for Analytical Instruments.
  • Standard, high performing versions for Industrial applications.
APDs are widely used in instrumentation and aerospace applications, offering a combination of high speed and high sensitivity

Long Wavelength 1060nm Enhanced APDs Excelitas’ C30954EH, C30955EH, and C30956EH are general purpose silicon avalanche photodiodes made using a double-diffused "reach through" structure. The design of these photodiodes is such that their long wave response (i.e. > 900 nm) has been enhanced without introducing any undesirable properties.
LLAM The LLAM series of Silicon and InGaAs avalanche photodiodes (APD) receiver modules feature an APD, thermoelectric cooler (TEC) and a hybrid, all in the same hermetically-sealed modified 12-lead TO-66 flange package for increased heat sinking. The use of a TEC eases the burden on the APD bias control to insure constant responsivity over a 5°C to 40°C ambient temperature range.
Analytical and Industrial Applications

These rear entry “reach-through” silicon APDs offer the best compromise in terms of cost and performance for applications requiring high speed and low noise photon detection from 400 nm up to 1100 nm. They feature low noise, high quantum efficiency and high gain while maintaining reasonably low operating voltage.

APDs for Rangefinding

The Excelitas C30737 series silicon APDs provide high responsivity between 500 nm and 1000 nm as well as extremely fast rise times at all wavelengths, with a frequency response above 1 GHz for bandwidth-optimised versions. The C30724, as a low gain APD, can be operated at a fixed voltage without the need for temperature compensation.

UV Enhanced APDs

The C30739ECERH Silicon Avalanche Photodiode (APD) is intended for use in a wide variety of broadband low light level applications covering the spectral range from below 400 to over 700 nm. It has low noise, low capacitance and high gain. It is designed to have an enhanced short wavelength sensitivity, with quantum efficiency of 60 % at 430 nm.

InGaAs APDs

The C30644, C30645 and C30662 Series APDs are high speed, large area InGaAs/lnP avalanche photodiodes. These devices provide large quantum efficiency, (QE), high responsivity and low noise in the spectral range between 1100 nm and 1700 nm, with standard active areas up to 200 µm in diameter. They are optimized for use at a wavelength of 1550 nm, ideally suitable for use in eye-safe laser range finding systems.

APD Arrays

The C30927 series of quadrant Si Avalanche Photodiode and the C30985E multi-element APD array utilize the double-diffused “reach-through” structure. This structure provides ultra high sensitivity at 400-1000 nm.