KETEK's SiPM data sheets detail key performance parameters of their silicon photomultipliers - the effects of temperature on the performance of the SiPM can be important and are discussed here.
Silicon Photomultipliers have a positive temperature coefficient of the breakdown voltage - the breakdown voltage increases with increasing temperature.
As a result the applied overvoltage is effectively reduced if temperature increases and the applied bias voltage remains unchanged - hence Gain, which is proportional to the overvoltage, will reduce if temperature increases and the bias voltage is not adjusted accordingly.
The relationship between breakdown voltage and temperature is linear - for KETEK SiPMs the figure is ~22mV/°C - as described in the following equation:-
|1/G · (δG/δT) = -1/V · (δVBD/δT) ≈ -22mV/δT · K-1|
|G = Gain||ΔV = Overvoltage||VBD = Breakdown Voltage||T = Temperature|
However, as Gain is proportional to overvoltage, and the ratio of this 22mV figure to the overvoltage reduces with increasing overvoltage, it can be seen that the temperature coefficient of Gain decreases with increasing overvoltage. The graph below shows the temperature coefficient of Gain versus relative overvoltage for KETEK's EB-Series SiPMs - it is correct for the current WB-Series.
The low temperature dependency (22mV/°C) of KETEK's SiPMs can make adjustment of the bias voltage with temperature unnecessary, reducing system complexity and cost. In cases where precise control of the overvoltage (Gain) is required, such as spectroscopic radiation detection where it is desirable to keep a given energy within the same MCA channel, the low figure reduces the voltage compliance necessary.