1,523 research outputs found
Compact CMOS active quenching/recharge circuit for SPAD arrays
Avalanche diodes operating in Geiger mode are able to detect single photon events. They can be employed to photon counting and time-of-flight estimation. In order to ensure proper operation of these devices, the avalanche current must be rapidly quenched, and, later on, the initial equilibrium must be restored. In this paper, we present an active quenching/recharge circuit specially designed to be integrated in the form of an array of single-photon avalanche diode (SPAD) detectors. Active quenching and recharge provide benefits like an accurately controllable pulse width and afterpulsing reduction. In addition, this circuit yields one of the lowest reported area occupations and power consumptions. The quenching mechanism employed is based on a positive feedback loop that accelerates quenching right after sensing the avalanche current. We have employed a current starved inverter for the regulation of the hold-off time, which is more compact than other reported controllable delay implementations. This circuit has been fabricated in a standard 0.18 μm complementary metal-oxide-semiconductor (CMOS) technology. The SPAD has a quasi-circular shape of 12 μm diameter active area. The fill factor is about 11%. The measured time resolution of the detector is 187 ps. The photon-detection efficiency (PDE) at 540 nm wavelength is about 5% at an excess voltage of 900 mV. The break-down voltage is 10.3 V. A dark count rate of 19 kHz is measured at room temperature. Worst case post-layout simulations show a 117 ps quenching and 280 ps restoring times. The dead time can be accurately tuned from 5 to 500 ns. The pulse-width jitter is below 1.8 ns when dead time is set to 40 ns.Ministerio de EconomÃa y Competitividad TEC2012-38921-C02, IPT-2011-1625-430000, IPC-20111009 CDTIJunta de AndalucÃa TIC 2338-2013Office of Naval Research (USA) N00014141035
SPAD Figures of Merit for Photon-Counting, Photon-Timing, and Imaging Applications: A Review
Single-photon avalanche diodes (SPADs) emerged as the most suitable photodetectors for both single-photon counting and photon-timing applications. Different complementary metal-oxide-semiconductor (CMOS) devices have been reported in the literature, with quite different performance and some excelling in just few of them, but often at different operating conditions. In order to provide proper criteria for performance assessment, we present some figures of merit (FoMs) able to summarize the typical SPAD performance (i.e., photon detection efficiency, dark counting rate, afterpulsing probability, hold-off time, and timing jitter) and to identify a proper metric for SPAD comparisons, when used either as single-pixel detectors or in imaging arrays. The ultimate goal is not to define a ranking list of best-in-class detectors, but to quantitatively help the end-user to state the overall performance of different SPADs in either photon-counting, timing, or imaging applications. We review many CMOS SPADs from different research groups and companies, we compute the proposed FoMs for all them and, eventually, we provide an insight on present CMOS SPAD technologies and future trends
Geiger-Mode Avalanche Photodiodes in Standard CMOS Technologies
Photodiodes are the simplest but most versatile semiconductor optoelectronic devices. They
can be used for direct detection of light, of soft X and gamma rays, and of particles such as
electrons or neutrons. For many years, the sensors of choice for most research and industrial
applications needing photon counting or timing have been vacuum-based devices such as
Photo-Multiplier Tubes, PMT, and Micro-Channel Plates, MCP (Renker, 2004). Although
these photodetectors provide good sensitivity, noise and timing characteristics, they still
suffer from limitations owing to their large power consumption, high operation voltages
and sensitivity to magnetic fields, as well as they are still bulky, fragile and expensive. New
approaches to high-sensitivity imagers tend to use CCD cameras coupled with either MCP
Image Intensifiers, I-CCDs, or Electron Multipliers, EM-CCDs (Dussault & Hoess, 2004), but
they still have limited performances in extreme time-resolved measurements.
A fully solid-state solution can improve design flexibility, cost, miniaturization, integration
density, reliability and signal processing capabilities in photodetectors. In particular, Single-
Photon Avalanche Diodes, SPADs, fabricated by conventional planar technology on silicon
can be used as particle (Stapels et al., 2007) and photon (Ghioni et al., 2007) detectors with
high intrinsic gain and speed. These SPAD are silicon Avalanche PhotoDiodes biased above
breakdown. This operation regime, known as Geiger mode, gives excellent single-photon
sensitivity thanks to the avalanche caused by impact ionization of the photogenerated
carriers (Cova et al., 1996). The number of carriers generated as a result of the absorption of
a single photon determines the optical gain of the device, which in the case of SPADs may
be virtually infinite.
The basic concepts concerning the behaviour of G-APDs and the physical processes taking
place during their operation will be reviewed next, as well as the main performance
parameters and noise sources
Single-Photon Avalanche Diodes in a 0.16 μm BCD Technology With Sharp Timing Response and Red-Enhanced Sensitivity
CMOS single-photon avalanche diodes (SPADs) have recently become an emerging imaging technology for applications requiring high sensitivity and high frame-rate in the visible and near-infrared range. However, a higher photon detection efficiency (PDE), particularly in the 700-950 nm range, is highly desirable for many growing markets, such as eye-safe three-dimensional imaging (LIDAR). In this paper, we report the design and characterization of SPADs fabricated in a 0.16 mu m BCD (Bipolar-CMOS-DMOS) technology. The overall detection performance is among the best reported in the literature: 1) PDE of 60% at 500 nm wavelength and still 12% at 800 nm; 2) very low dark count rate of < 0.2 cps/mu m(2) (in counts per second per unit area); 3) < 1% afterpulsing probability with 50 ns dead-time; and 4) temporal response with 30 ps full width at half-maximum and less than 50 ps diffusion tail time constant
Feasibility of Geiger-mode avalanche photodiodes in CMOS standard technologies for tracker detectors
The next generation of particle colliders will be characterized by linear lepton colliders, where the collisions between electrons and positrons will allow to study in great detail the new particle discovered at CERN in 2012 (presumably the Higgs boson). At present time, there are two alternative projects underway, namely the ILC (International Linear Collider) and CLIC (Compact LInear Collider). From the detector point of view, the physics aims at these particle colliders impose such extreme requirements, that there is no sensor technology available in the market that can fulfill all of them. As a result, several new detector systems are being developed in parallel with the accelerator.
This thesis presents the development of a GAPD (Geiger-mode Avalanche PhotoDiode) pixel detector aimed mostly at particle tracking at future linear colliders. GAPDs offer outstanding qualities to meet the challenging requirements of ILC and CLIC, such as an extraordinary high sensitivity, virtually infinite gain and ultra-fast response time, apart from compatibility with standard CMOS technologies. In particular, GAPD detectors enable the direct conversion of a single particle event onto a CMOS digital pulse in the sub-nanosecond time scale without the utilization of either preamplifiers or pulse shapers. As a result, GAPDs can be read out after each single bunch crossing, a unique quality that none of its competitors can offer at the moment. In spite of all these advantages, GAPD detectors suffer from two main problems. On the one side, there exist noise phenomena inherent to the sensor, which induce noise pulses that cannot be distinguished from real particle events and also worsen the detector occupancy to unacceptable levels. On the other side, the fill-factor is too low and gives rise to a reduced detection efficiency.
Solutions to the two problems commented that are compliant with the severe specifications of the next generation of particle colliders have been thoroughly investigated. The design and characterization of several single pixels and small arrays that incorporate some elements to reduce the intrinsic noise generated by the sensor are presented. The sensors and the readout circuits have been monolithically integrated in a conventional HV-CMOS 0.35 μm process. Concerning the readout circuits, both voltage-mode and current-mode options have been considered. Moreover, the time-gated operation has also been explored as an alternative to reduce the detected sensor noise. The design and thorough characterization of a prototype GAPD array, also monolithically integrated in a conventional 0.35 μm HV-CMOS process, is presented in the thesis as well. The detector consists of 10 rows x 43 columns of pixels, with a total sensitive area of 1 mm x 1 mm. The array is operated in a time-gated mode and read out sequentially by rows. The efficiency of the proposed technique to reduce the detected noise is shown with a wide variety of measurements. Further improved results are obtained with the
reduction of the working temperature. Finally, the suitability of the proposed detector array for particle detection is shown with the results of a beam-test campaign conducted at CERN-SPS (European Organization for Nuclear Research-Super Proton Synchrotron). Apart from that, a series of additional approaches to improve the performance of the GAPD technology are proposed. The benefits of integrating a GAPD pixel array in a 3D process in terms of overcoming the fill-factor limitation are examined first. The design of a GAPD detector in the Global Foundries 130 nm/Tezzaron 3D process is also presented. Moreover, the possibility to obtain better results in light detection applications by means of the time-gated operation or correction techniques is analyzed too.Aquesta tesi presenta el desenvolupament d’un detector de pÃxels de GAPDs (Geiger-mode Avalanche PhotoDiodes) dedicat principalment a rastrejar partÃcules en futurs col•lisionadors lineals. Els GAPDs ofereixen unes qualitats extraordinà ries per satisfer els requisits extremadament exigents d’ILC (International Linear Collider) i CLIC (Compact LInear Collider), els dos projectes per la propera generació de col•lisionadors que s’han proposat fins a dia d’avui. Entre aquestes qualitats es troben una sensibilitat extremadament elevada, un guany virtualment infinit i una resposta molt rà pida, a part de ser compatibles amb les tecnologies CMOS està ndard. En concret, els detectors de GAPDs fan possible la conversió directa d’un esdeveniment generat per una sola partÃcula en un senyal CMOS digital amb un temps inferior al nanosegon. Com a resultat d’aquest fet, els GAPDs poden ser llegits després de cada bunch crossing (la col•lisió de les partÃcules), una qualitat única que cap dels seus competidors pot oferir en el moment actual. Malgrat tots aquests avantatges, els detectors de GAPDs pateixen dos grans problemes. D’una banda, existeixen fenòmens de soroll inherents al sensor, els quals indueixen polsos de soroll que no poden ser distingits dels esdeveniments reals generats per partÃcules i que a més empitjoren l’ocupació del detector a nivells inacceptables. D’altra banda, el fill-factor (és a dir, l’à rea sensible respecte l’à rea total) és molt baix i redueix l’eficiència detectora.
En aquesta tesi s’han investigat solucions als dos problemes comentats i que a més compleixen amb les especificacions altament severes dels futurs col•lisionadors lineals. El detector de pÃxels de GAPDs, el qual ha estat monolÃticament integrat en un procés HV-CMOS està ndard de 0.35 μm, incorpora circuits de lectura en mode voltatge que permeten operar el sensor en l’anomenat mode time-gated per tal de reduir el soroll detectat. L’eficiència de la tècnica proposada queda demostrada amb la gran varietat d’experiments que s’han dut a terme. Els resultats del beam-test dut a terme al CERN indiquen la capacitat del detector de pÃxels de GAPDs per detectar partÃcules altament energètiques. A banda d’això, també s’han estudiat els beneficis d’integrar un detector de pÃxels de GAPDs en un procés 3D per tal d’incrementar el fill-factor. L’anà lisi realitzat conclou que es poden assolir fill-factors superiors al 90%
Enhancing the fill-factor of CMOS SPAD arrays using microlens integration
Arrays of single-photon avalanche diode (SPAD) detectors were fabricated, using a 0.35 μm CMOS technology process,
for use in applications such as time-of-flight 3D ranging and microscopy. Each 150 x 150 μm pixel comprises a 30 μm
active area diameter SPAD and its associated circuitry for counting, timing and quenching, resulting in a fill-factor of
3.14%. This paper reports how a higher effective fill-factor was achieved as a result of integrating microlens arrays on
top of the 32 x 32 SPAD arrays. Diffractive and refractive microlens arrays were designed to concentrate the incoming
light onto the active area of each pixel. A telecentric imaging system was used to measure the improvement factor (IF)
resulting from microlens integration, whilst varying the f-number of incident light from f/2 to f/22 in one-stop
increments across a spectral range of 500-900 nm. These measurements have demonstrated an increasing IF with fnumber,
and a maximum of ~16 at the peak wavelength, showing a good agreement with theoretical values. An IF of 16
represents the highest value reported in the literature for microlenses integrated onto a SPAD detector array. The results
from statistical analysis indicated the variation of detector efficiency was between 3-10% across the whole f-number
range, demonstrating excellent uniformity across the detector plane with and without microlenses
A 64x64 SPAD array for portable colorimetric sensing, fluorescence and X-ray imaging
We present the design and application of a 64x64 pixel SPAD array to portable colorimetric sensing, and fluorescence and x-ray imaging. The device was fabricated on an unmodified 180 nm CMOS process and is based on a square p+/n active junction SPAD geometry suitable for detecting green fluorescence emission. The stand-alone SPAD shows a photodetection probability greater than 60% at 5 V excess bias, with a dark count rate of less than 4 cps/µm2 and sub-ns timing jitter performance. It has a global shutter with an in-pixel 8-bit counter; four 5-bit decoders and two 64-to-1 multiplexer blocks allow the data to be read-out. The array of sensors was able to detect fluorescence from a fluorescein isothiocyanate (FITC) solution down to a concentration of 900 pM with a SNR of 9.8 dB. A colorimetric assay was performed on top of the sensor array with a limit of quantification of 3.1 µM. X-rays images, using energies ranging from 10 kVp to 100 kVp, of a lead grating mask were acquired without using a scintillation crystal
Monolithic Perimeter Gated Single Photon Avalanche Diode Based Optical Detector in Standard CMOS
Since the 1930\u27s photomultiplier tubes (PMTs) have been used in single photon detection. Single photon avalanche diodes (SPADs) are p-n junctions operated in the Geiger mode. Unlike PMTs, CMOS based SPADs are smaller in size, insensitive to magnetic fields, less expensive, less temperature dependent, and have lower bias voltages. Using appropriate readout circuitry, they measure properties of single photons, such as energy, arrival time, and spatial path making them excellent candidates for single photon detection. CMOS SPADs suffer from premature breakdown due to the non-uniform distribution of the electric field. This prevents full volumetric breakdown of the device and reduces the detection effciency by increasing the noise. A novel device known as the perimeter gated SPAD (PGSPAD) is adopted in this dissertation for mitigating the premature perimeter breakdown without compromising the fill-factor of the device. The novel contributions of this work are as follows.
A novel simulation model, including SPICE characteristics and the stochastic behavior, has been developed for the perimeter gated SPAD. This model has the ability to simulate the static current-voltage and dynamic response characteristics. It also simulates the noise and spectral response.
A perimeter gated silicon photomultiplier, with improved signal to noise ratio, is reported for the first time. The gate voltage reduces the dark current of the silicon photomultiplier by preventing the premature breakdown.
A digital SPAD with the tunable dynamic range and sensitivity is demonstrated for the first time. This pixel can be used for weak optical signal application when relatively higher sensitivity and lower input dynamic range is required. By making the sensitivity-dynamic range trade-off the same detector can be used for applications with relatively higher optical power.
Finally, an array has been developed using the digital silicon photomultiplier in which the dead time of the pixels have been reduced. This digital photomultiplier features noise variation compensation between the pixels
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