Avalanche photodiodes (APDs) are very sensitive semiconductors that exploit the photoelectric effect to convert light to electricity and are the semiconductor analogue of photomultipliers. Their spectral response depends upon the substrate used, for example, silicon detects in the ~150-1100 nm region, whilst InGaAs extends to 1.7 µm.
Large area APDs, with active areas reaching 16 mm diameter, offer significant performance advantages over photomultiplier tube (PMT) technologies by not using fragile glass envelopes, and the semiconductor technology allows LAAPDs to be significantly smaller and offer unrivalled quantum efficiency at the DUV region. These Si-based windowless non-cooled devices offer high gain and low noise, in a SHV (safe high voltage) package.
