Monolithic CMOS detector module for photon counting and picosecond timing

Abstract

A monolithic optoelectronic module.for counting and timing single optical photons has been designed and fabricated in CMOS technology It integrates a SinglePhoton Avalanche Diode (SPAD) ofl2pm-diameter with a complete active-quenching and active-reset circuit. The detector operates in Geiger-mode biased above breakdown level, with overvoltage adjustable up to 20V. The on-chip electronics detects the rise of the current triggered by a photogenerated carrier, then swftly quenches the avalanche by controlling the SPAD bias voltage. and finally resets the detector after a hold-off time (adjustablefrom 0 to 350ns). Thefast sensing stage limits the avalanche charge and hence the afterpulsing probability, which is further reduced below 0.02% by exploiting the hold-off fzature. Good photon detection efficiency (above 20% over all the range from 400nm to 700nm. with 40% peak at 500nm) is obtained together with low intrinsic detector noise (dark counting rate lower than 600cps at 5V excess bias voltage). In a chip of 700pm x 1.000pm, the overall performance is comparable or better than that of macroscopic modules available from leading industries. Single Photon Detectors and CircuitsPhoton-counting modules are required in many industrial and scientific applications like: time-of-flight, quantum cryptography, particle sizing, fluorescence spectrometry, single molecule detection, etc. The basic requirements are adequate active area (at least a few tens of micron diameter), low noise (below Ikcps), small time jitter (few tens of ps), good detection efficiency in the visible and near-infrared range.Photomultiplier tubes can detect ultraweak and ultrafast optical signals, hut they are bulky, delicate and sensitive to magnetic fields, require high voltage supply and signal conditioning. Ordinary avalanche photodiodes (APD) offer the advantage of solid-state devices, hut they have limited gain and high excess noise. Singlephoton avalanche diodes (SPAD) [l] attain the ultimate sensitivity and detect single photons by exploiting the positive feedback in avalanche multiplication above the breakdown level. SPAD devices have been fabricated in different technologies: reach-through dedicated 121 131, planar 141 and CMOS-like 151 [6]. 341The self-sustaining avalanche process must he quenched and the SPAD must then he reset to quiescent level. Simple passive quenching [7] is obtained with a high-value ballast resistance, hut it is the ActiveQuenching Circuit (AQC) concept [ l ] that made possible to exploit at hest the SPAD performance [7]. Various discrete-component AQCs have heen reported [I] [2], 181, 191; attempts to integrate detector and electronics have also been reported. Ref.[10] presents a circuit with passive quenching and active reset, integrated with a SPAD of 3pm-diameter operating with only 2.5V overvoltage. Ref. 151 reports arrays of SPADs with 3V overvoltage, integrated with digital CMOS circuitry for measuring photon arrival times with 700ps timing resolution.In these cases, the current onset was sensed by means of simp...

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