Single Photon Sensitive Avalanche Photodiodes
As a leading developer of electro-optical devices and optical instrumentation products, Voxtel focuses on developing advanced avalanche photodiodes (APDs) that provide performance not available from other vendors. Most commercial APDs that are responsive in the near infrared (NIR) were developed for telecommunications and, therefore, are not optimized for demanding photon counting applications like laser radar (LADAR), fluorescence spectroscopy, and quantum information. We serve a variety of industrial, scientific, and military markets with photon-counting APDs fabricated from silicon and III-V compound semiconductor alloys, covering the 190 – 1600 nm spectral range.
APDs are notable among semiconductor photodetectors in that they provide internal gain. APDs operated in ‘linear mode’ have a proportional response to light and can amplify a small initial photocurrent by a factor of over 1000; APDs operated in ‘Geiger mode’ can generate current pulses in response to single photons that are easily detected. Thus, APDs are the most sensitive of the common solid state photodetectors available.
Generally, silicon APDs are used for photo response between 190 and 1100 nm, although their efficiency drops rapidly at wavelengths longer than 1000 nm. For NIR applications between 1000 and 1600 nm, APD products based upon InGaAs absorbers are much more efficient. InGaAsP APDs were developed to cover this spectral range for the telecommunications market, but they are typically operated around a gain of just 10 and are not optimized for applications requiring high sensitivity. In addition to silicon and InGaAsP products, Voxtel manufactures AlGaInAs APDs to cover the NIR.
