Microcell Construction

The KETEK SiPMs are available in two basic Technologies:

Ketek Standard Technology
Ketek Trench Technology

Technology optimized for maximum GE

Technology with improved optical barrier and low-RC readout

Devices with very high PDE

Devices with low noise and improved timing

Particularly suitable for small microcells and small active area

Particularly suitable for large microcells and large area devices

KETEK Standard Technology

KETEK Silicon Photomultipliers are based on a P-on-N structure: A shallow, highly P-doped region on top of a low N-doped common silicon body is forming the entrance window for the incoming light (Figure 1).

Figure 1: Cross section of micro cells processed in Standard Technology.

For this structure nearly all Avalanche breakdowns, caused by blue- and UV light, are triggered by electrons. Due to the higher ionization coefficients for electrons the silicon P-on-N structure has a higher Geiger efficiency for blue- and UV light compared to a N-on-P structure. In addition, the dead layer of the PN-junction and the geometrical fill factor of the microcell have been continuously improved over the last years. Therefore KETEK is able to present Silicon Photomultipliers with the highest PDE values for blue light.

The quenching resistor of a KETEK Silicon Photomultiplier is formed by a doped polysilicon strip line embedded in an insulating matrix. The resistivity can be precisely adjusted in a range starting from 100 kΩ up to several MΩ.

The entrance window of the light sensitive PN-junction is coated with an antireflective layer with maximum transmission for blue light to avoid any reflection light losses at the interface.

KETEK Trench Technology

In order to reduce the optical cross talk probability between individual microcells KETEK has introduced a very narrow vertical trench technology (Figure 2) for its devices.

Figure 2: Cross section of micro cells processed in Trench Technology.

The trench is completely surrounding each microcell.

Together with the trench technology an effective impurity gettering has been implemented and the parasitic RC-values have been further reduced.

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