Proceedings Article | 28 April 2010
Proc. SPIE. 7681, Advanced Photon Counting Techniques IV

KEYWORDS: Ionization, Lead, Photon counting, Electrons, Avalanche photodiodes, Picosecond phenomena, Single photon, Quantum efficiency, Silicon, Performance modeling

Important avalanche breakdown statistics for Single Photon Avalanche Diodes (SPADs), such as avalanche breakdown
probability, dark count rate, and the distribution of time taken to reach breakdown (providing mean time to breakdown
and jitter), were simulated. These simulations enable unambiguous studies on effects of avalanche region width,
ionization coefficient ratio and carrier dead space on the avalanche statistics, which are the fundamental limits of the
SPADs. The effects of quenching resistor/circuit have been ignored. Due to competing effects between dead spaces,
which are significant in modern SPADs with narrow avalanche regions, and converging ionization coefficients, the
breakdown probability versus overbias characteristics from different avalanche region widths are fairly close to each
other. Concerning avalanche breakdown timing at given value of breakdown probability, using avalanche material with
similar ionization coefficients yields fast avalanche breakdowns with small timing jitter (albeit higher operating field),
compared to material with dissimilar ionization coefficients. This is the opposite requirement for abrupt breakdown
probability versus overbias characteristics. In addition, by taking band-to-band tunneling current (dark carriers) into
account, minimum avalanche region width for practical SPADs was found to be 0.3 and 0.2 μm, for InP and InAlAs,
respectively.