We are reporting time resolved photon counting performance of several types of single photon avalanche detectors (SPAD) employed to detection in near infrared wavelength region. The main application goal is the quantum cryptography operating at the 1550 nm wavelength region.

SPAD are based on avalanche photodiode. It works biased in backward direction above the breakdown voltage, the detector current remains zero until a carrier reaches the high field region of the p-n junction and trigger the avalanche multiplication process. The current quickly reaches the macroscopic value. After this diode must be quenched by lowering the bias below breakdown level. The principle of the SPADs is the temporal correlation between photon absorption induced first carrier generation and the leading edge of the avalanche current pulse.

The Silicon is the most used semiconductor for avalanche photodiode construction. It is due to propitious ration between coefficients of impact ionization of electrons and holes. The disproportion between these coefficients enable quick avalanche grows. Unfortunately, Germanium and InGaAs as semiconductors that have useful quantum efficiency absorption in near infra and the technology of that is quite sophisticated, have ratio of this two coefficients close one. This problem is particularly solved by multi-layer structure. The result of this inherent property is lower amplitude of current pulse, it is lower amplification of avalanche, and its slower leading edge.

Test of following avalanche photodiodes in photon counting mode are presented. Ge photodiodes (own construction), InGaAs/InP Fujitsu and EG&G InGaAs diode chips. Diodes are operated in passive and active quenching mode, in wide temperature range from 77K to room temperature using close cycle Helium cryocooler. The dark noise and temporal resolution was observed as resultant parameters for each configuration. The recommendation for construction of new gating and quenching circuit designed for Germanium and InGaAs avalanche photodiodes is summarized in conclusion.

References

This research has been conducted within the framework of CTU research project J04/98:210000022

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