We are presenting the results of the study of the Single Photon Avalanche Diode (SPAD) pulse response risetime and its dependence on several key parameters. We were investigating the unique properties of K14 type SPAD with its high delay uniformity of 200 μm active area and the correlation between the avalanche buildup time and the photon number involved in the avalanche trigger. The detection chip was operated in a passive quenching circuit with active gating. This setup enabled us to monitor the diode reverse current using an electrometer, a fast digitizing oscilloscope, and using a custom design comparator circuit. The electrometer reading enabled to estimate the photon number per detection event, independently on avalanche process. The avalanche build up was recorded on the oscilloscope and processed by custom designed waveform analysis package. The correlation of avalanche build up to the photon number, bias above break, photon absorption location, optical pulse length and photon energy was investigated in detail. The experimental results are presented. The existing solid state photon counting detectors have been dedicated for picosecond resolution and timing stability of single photon events. However, the high timing stability is maintained for individual single photons detection, only. If more than one photon is absorbed within the detector time resolution, the detection delay will be significantly affected. This fact is restricting the application of the solid state photon counters to cases where single photons may be guaranteed, only. For laser ranging purposes it is highly desirable to have a detector, which detects both single photon and multi photon signals with picoseconds stability. The SPAD based photon counter works in a purely digital mode: a uniform output signal is generated once the photon is detected. If the input signal consists of several photons, the first absorbed one triggers the avalanche. Obviously, for multiple photon signals, the detection delay will be shorter in comparison to the single photon events. The detection delay dependence on the optical input signal strength is called the "detector time walk". To enable the detector operation in both the single and multi photon signal regime with a minimal time walk, a time walk compensation technique has been developed in nineties.

Date Published: 6 August 2009
PDF: 7 pages
Proc. SPIE 7384, International Symposium on Photoelectronic Detection and Imaging 2009: Advances in Imaging Detectors and Applications, 73841I (6 August 2009); doi: 10.1117/12.835564

Published in SPIE Proceedings Vol. 7384:
International Symposium on Photoelectronic Detection and Imaging 2009: Advances in Imaging Detectors and Applications
Kun Zhang; Xiang-jun Wang; Guang-jun Zhang; Ke-cong Ai, Editor(s)