Speaker
Dr
Fabrice Retiere
(TRIUMF)
Description
Hamamatsu Photonics Multi-Pixel Photon Counters (MPPCs) achieve high photodetection efficiency with relativelity low dark noise. The MPPC gain is comparable to Photomultipliers but but the pixel avalanches tend to trigger others either in neighboring pixels (crosstalk) or in the same pixel at a latter time (after-pulsing). Cross-talk and after-pulsing avalanches are one of the main limitation of MPPCs preventing operation at large operating voltage. Crosstalk avalanches are thought to be due to optical photons created in the avalanche and absorbed in a neighboring pixels. On the other hand, after-pulsing avalanches are thought to be due to charge carriers produced in the avalanches that become trapped on impurities and released at latter time. We investigate the possibility that after-pulsing avalanches are also due to visible photons created in the avalanches but absorbed in the silicon bulk rather than in neighboring pixel high field region. Then, the charge carriers created in the silicon bulk diffuse back to the high field region, yielding delayed avalanches. The MPPCs were illuminated with laser light at wavelength ranging from 404 to 820 nm and the timing distribution of the avalanches was measured. Delayed avalanches were observed at 637 and 820 nm showing that some holes do diffuse to the high field region. Simulations show that optical photons are responsible for at least half of the after-pulsing avalanches. The data also shows that the MPPC single photon timing resolution cannot be described by a simple Gaussian distribution.
Author
Dr
Fabrice Retiere
(TRIUMF)
Co-author
Mr
Kyle Boone
(University of British Columbia)
