Silicon Photomultiplier: Everything You Need to Know
Silicon photomultiplier (SiPM) technology improves timing and sensitivity of applications that involve photon detection. These sensors are useful for detecting light wavelengths in the near-ultraviolet to near-infrared range. As a solid-state device solution with no moving parts, SiPM is more efficient than heavier photomultiplier tubes when it comes to sensing, quantifying, and timing various levels of light.
SiPM Technology Benefits
An SiPM is a compact device with a series of hundreds of thousands of microcells known as single-photon avalanche photodiodes (SAPDs). Each SAPD consists of an integrated series of quenching resistors plus a positive and negative terminal. Certain manufacturers such as SensL use a third terminal with a fast output capacitor. These sensors are activated above breakdown voltage (VBD).
One of the key advantages of SiPMs is that they can detect a wide range of photons, ranging from as low as one photon to as many as several thousands in an application. Due to their ability to withstand mechanical shocks, these sensors can be used for a wide range of light detection applications. They are particularly useful when it's necessary to track the precision timing of photons.
SiPMs are used for 3D ranging, sorting and recycling and threat detection, among many other applications. Silicon photomultipliers are commonly used in the oil, aerospace, automotive, electronic components and communication industries. The design and size of the sensor are usually customized to fit a specific device. While miniature sensors are used for UAV applications, field gamma spectroscopy operations require larger sensors.
How the Silicon Photomultiplier Works
A switch remains open when no light appears on the microcell,. When a photon is captured by microcell, it creates an electron-hole pair. A charge carrier then triggers a self-sustaining avalanche process and continuous current flow until quenching. The VBD is the minimum bias voltage that occurs during the self-sustaining multiplication. When the VBIAS exceeds the VBD, the SAPD generates a current pulse. The excess voltage then controls the SiPM operation.
Overvoltage can enhance PDE and SiPM performance, but at a certain level above the noise, interference and temperature become a concern. Breakdown voltage increases at higher temperatures, affecting gain and photon detection.