Avalanche Photodiodes (APDs)
Silicon avalanche photodiodes (APDs) can be considered a solid-state replacement for traditional photomultiplier tubes (PMTs). Both detectors create signal gain by the impact ionization process within the device. However, unlike PMTs, APDs can directly detect both photons (low energy x-rays and UV/optical photons) and ionizing particles, while a PMT can only directly detect optical photons. For the detection of gamma-rays, APDs (and PMTs) need to be optically combined with a scintillation medium. APDs are also much thinner and more compact than PMTs, and are insensitive to magnetic fields.
RMD’s silicon APDs, when a high bias voltage is applied, can achieve and sustain a relatively high gain because they are fabricated using a deep diffused planar manufacturing process. Additionally, like other solid-state detectors, RMD’s APDs have a high quantum detection efficiency and a wide spectral response. RMD’s APDs can be fabricated as discrete devices, arrays, and position sensitive structures. APD chips are mounted on ceramic substrates with rigid conducting pins for signal readout and biasing.
APD manufactured using a deep diffusion process