#Dark noise avalanche vs photodiode for free#

The multiplication region M is designed to exhibit a high electric field so as to provide internal photo-current gain by impact ionization. Present across region A is an electric field E that serves to separate the photo-generated holes and electrons, and sweeps one carrier towards the multiplication region. The basic structural elements provided by the APD designer include an absorption region A, and a multiplication region M. What some of these trade-offs are, and how they are optimized in commercially available APDs, are listed below.Ĭonsider the schematic cross-section for a typical APD structure shown in Figure 1. More simply, an ideal APD would be a good PIN photodiode with gain! In reality however, this is difficult to achieve because of the need to trade-off conflicting design requirements. The ideal APD would have zero dark noise, no excess noise, broad spectral and frequency response, a gain range from 1 to 106 or more, and low cost. In order to understand why more than one APD structure exists, it is important to appreciate the design trade-offs that must be accommodated by the APD designer. Photon-counting detection efficiencies > 70% at 633 nm dark counts of only 1 count/s on 150 µm diameter APDsĭetection and resolution of low energy, 1 to 30 keV X-rays Noise equivalent power (NEP) of Detection of 100-photon, 20 ns pulses with standard APDsĭetection of 10-photon, 20 ns pulses with special APDsīER data communications at 810 nm at 60 Mb/s with only 39 photons/bit Typical demonstrated APD performance includes:

#Dark noise avalanche vs photodiode for free#

APD Performance for Free Space Optics / Optical Wireless A germanium APD is recommended for environmental applications in high electromagnetic interference (EMI), where amplifier noise is significantly higher than the noise from an InGaAs APD, or for applications where cost is primordial consideration. Silicon APDs can be used between 300 to 1100 nm, germanium between 8 nm and InGaAs from 900 to 1700 nm.Īlthough significantly more expensive than germanium APDs, InGaAs APDs are typically available with significantly lower noise current, exhibit extended spectral response to 1700 nm, and provide higher frequency bandwidth for a given active area. Silicon Avalanche photodiodes are commercially available that span the wavelength range from 300 to 1700 nm. APDs are widely used in instrumentation and aerospace applications, offering a combination of high speed and high sensitivity unmatched by PIN detectors. FSO/Laser Links have to operate in variety of “Atmospheric Fade” conditions including Fog, Dust Storms, Snow, Ice, Rain and Smog.įor low-light detection in the 200 to 1150 nm range, the designer has two basic detector choices – the silicon PIN detector, or the silicon avalanche photodiode (APD). Ideal for Low Light Detection to overcome thick Fog and other Fade effects Free Space Optical link with APD receiverįree Space Optics (FSO) is almost always a photon-scarce application, requiring low light detection technology – to ensure link availability and enhance range.

OFDM (Orthogonal Frequency Division Multiplexing)ĪPD in Free Space Optics (FSO) ApplicationsĪvalanche photodiode detectors are used in many diverse applications such as Free Space Optics, laser range finders and photon correlation studies.

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