Silicon photomultiplier demonstrates its capabilities

A team from the Moscow Engineering and Physics Institute together with Pulsar Enterprise in Moscow have developed a silicon photomultiplier (SiPM), which promises a wide range of applications. The device is basically a large number (10³/mm²) of microphoton counters, which are located on a common silicon substrate and have a common output load. Each photon counter is a small (20-30 µm square) pixel with a depletion region of 2 µm. They are decoupled by polysilicon resistors and operate in a limited Geiger mode with a gain of 10⁶. This means that the SiPM is sensitive to a single photoelectron, with a very low noise level of less than 0.1 photoelectron. Although each SiPM pixel operates digitally as a binary device, as a whole the SiPM is an analogue detector that can measure light intensity within a dynamic range of about 10³/mm² and has excellent photon capability.

The photon detection efficiency of the SiPM is at the level of photomultiplier tubes (PMTs) in the blue region (20%), and is higher in the yellow-green region. The device has very good timing resolution (50 ps r.m.s. for one photoelectron) and shows very good temperature stability. It is also insensitive to magnetic fields. These characteristics mean that the SiPM can compete with other known photodetectors (e.g. PMT, APD, HPD, VLPC) and may prove useful for many applications, from very low light intensity detection in particle physics and astrophysics, through fast luminescence and fluorescence studies with low photon numbers in chemistry, biology and material science, to fast communication links.