Hole multiplication in a reverse-type avalanche photodiode

This paper reports on hole multiplication processes, detected in a reverse-type avalanche photodiode (APD), Hamamatsu Photonics type S8664-55, which has a light sensitive area of 5 × 5 mm and a depletion layer thickness of ∼ 40 μm. When the APD was irradiated from a Am isotope, the 13.9 keV and 17.6 keV X-rays produced spectral peaks, whose pulse height depended strongly on the bias voltage, whereas 57.5 keV photons produced another peak, whose the pulse height was much less bias sensitive. The former are identified with electron multiplication signals, whereas the latter with those due to hole multiplication. By measuring the electron and hole multiplication gains as a function of the bias voltage, the ratio of hole and electron ionization probabilities was determined as 0.0130 ± 0.0010 at 20 °C, and 0.0153 ±0.0010 at -20 °C.