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Crosstalk and afterpulsing in silicon photomultipliers can strongly limit the photon-counting resolution and dynamic range of the sensors. In this work we present a method and a measurement (as a demonstration) to separate the afterpulse and delayed crosstalk components of the delayed correlated pulses in STMicroelectronics silicon photomultiplier signals. The contribution of delayed crosstalk can be significant since even if one suppresses afterpulses by applying a longer recharge time, the delayed crosstalk component remains unaffected. This was the case for our measurement: 207 ns recharge was long enough to suppress afterpulses (3.3%), while the delayed crosstalk remained large (12.8%).

We report on the electrical and optical characterization, in continuous wave regime, of a novel class of silicon photomultipliers fabricated in standard planar technology on a silicon p-type substrate. Responsivity measurements, performed with an incident optical power down to tenths of picowatts, at different reverse bias voltages and on a broad (340–820 nm) spectrum, will be shown and discussed. The device temperature was monitored, allowing us to give a physical interpretation of the measurements. The obtained results demonstrate that such novel silicon photomultipliers are suitable as sensitive power meters for low photon fluxes.

Silicon photomultipliers (SiPMs) are fabricated in two different configurations: p-on-n and n-on-p junctions. p-on-n SiPMs turn out to be more suitable for application in positron emission tomography (PET), due to their higher sensitivity in blue wavelength range where common PET scintillators have their emission spectrum. In this paper, we report on the electro-optical performances of the first p-on-n SiPMs manufactured at STMicroelectronics, Catania. The results obtained on these devices are compared with those measured on the standard n-on-p technology.

We experimentally analyze the signal-to-noise ratio of continuous wave (CW) near infrared spectroscopy (NIRS) reflectance systems based on light emitting diodes and silicon photomultipliers for high performance low cost NIRS biomedical systems. We show that under suitable experimental conditions such systems exhibit a high SNR, which allows an SDS of 7 cm, to our knowledge the largest ever demonstrated in a CW-NIRs system. (C) 2016 Optical Society of America

In this paper the results of charge and timing resolution characterization realized at Fermi National Accelerator Laboratory (Fermilab) on 3.5 × 3.5 mm2 Silicon PhotoMultipliers fabricated at STMicroelectronics Catania R&D clean room facilities are presented. The device consists of 4900 microcells and has a geometrical fill factor of 36%. Timing measurements were realized at different wavelengths by varying the overvoltage and the temperature applied to the photodetector. The results shown in this manuscript demonstrate that the device, in spite of its large area, exhibits relevant features in terms of low dark current density, fast timing and very good single photoelectron resolution. All these characteristics can be considered very appealing in view of the utilization of this technology in applications requiring detectors with high timing and energy resolution performances.

In this paper we present the results of the first electrical and optical characterization performed on 1 mm2 total area Silicon Photomultipliers (SiPM) fabricated in standard silicon planar technology at the STMicroelectronics Catania R&D clean room facility. The device consists of 289 microcells and has a geometrical fill factor of 48%. Breakdown voltage, gain, dark noise rate, crosstalk, photon detection efficiency and linearity have been measured in our laboratories. The optical characterization has been performed by varying the temperature applied to the device. The results shown in the manuscript demonstrate that the device already exhibits relevant features in terms of low dark noise rate and inter-pixel crosstalk probability, high photon detection efficiency, good linearity and single photoelectron resolution. These characteristics can be considered really promising in view of the final application of the photodetector in the Positron Emission Tomography (PET).

In the framework of a national collaboration to bring Quantum Optics concepts to Astronomy, we are involved in finding suitable detectors for this novel application. At ‘INAF Osservatorio Astrofisico di Catania’ and ‘INFN – Laboratori Nazionali del Sud’ laboratories, measurements of electro-optical parameters, such as photon detection efficiency (PDE), linearity, dark counts and after pulsing probability, as well as of timing resolution, have been carried out. These measurements have been done on silicon detectors, such as single photon avalanche diode (SPAD) (both single element and array), and silicon photon multiplier (SiPM), operating in the photon counting regime.

The fabrication of silicon shallow junction photodiodes is a relevant topic for the detection of blue and near ultraviolet weak photon fluxes. In this paper we present a simple model to calculate the quantum detection efficiency (QDE) of a Geiger mode avalanche photodiode (GMAP) as a function of the dead layer thickness above the junction depletion layer. A comparison between calculated and experimental data is also presented. Moreover, by using the same model, an analysis of the QDE at 420 nm wavelength of conventional GMAPs based on shallow N+-P and P+-N junctions is given.

In this paper, we present the results of the first noise characterization performed on our novel 100-channel silicon photomultiplier. We have improved our previous single-photon avalanche photodiode technology in order to set up a working device with outstanding features in terms of single-photon resolving power up to R = 45, timing resolution down to 100 ps, and photon-detection efficiency of 14% at 420 nm. Tests were performed, and features were measured, as a function of the bias voltage and of the incident photon flux. A dedicated data-analysis procedure was developed that allows one to extract at once the relevant parameters and quantify the noise.

In this paper, we present the results of the charge and time characterization performed on our novel 100-channel silicon photomultiplier. We have improved our previous single-photon-avalanche-diode technology in order to set up a working device with outstanding features in terms of single-photon resolving power up to R = 45, a timing resolution down to 100 ps, and photon-detection efficiency of 14% at 420 nm. Tests were performed, and features were measured as a function of the bias voltage and of the incident photon flux. A dedicated data analysis procedure was developed that allows to extract at once the relevant parameters from the amplitude spectra and to determine the timing features.

In this paper, we present the results regarding the electrical and optical characterization of bidimensional arrays of silicon single photon avalanche photodiodes (SPAD). Low average dark count rates and crosstalk probability, good timing jitter and high quantum detection efficiency in the visible range have been measured over 5 × 5 SPAD arrays with 40 μm single pixel active area diameter. Moreover, a very good uniformity of these parameters has been found over the single pixels. These good electro-optical performances make our photodiodes attractive for the fabrication of arrays with a larger number of SPAD. In view of the design of a dense array to be used as a silicon photomultiplier (SiPM) for medical diagnostic tools, 5 × 5 SPAD arrays have been also tested in the photon-resolving mode. Charge spectra show that the arrays, in this configuration, allow to resolve several photoelectron peaks with a good single photoelectron resolution.

UNLABELLED We recently completed construction of a small-animal PET system-the MiniPET-3-that uses state-of-the-art silicon photomultiplier (SiPM) photosensors, making possible dual-modality imaging with MRI. In this article, we compare the MiniPET-3 with the MiniPET-2, a system with the same crystal geometry but conventional photomultiplier tubes (PMTs). METHODS The standard measurements proposed by the National Electrical Manufacturers Association NU 4 protocols were performed on both systems. These measurements included spatial resolution, system sensitivity, energy resolution, counting rate performance, scatter fraction, spillover ratio for air and water, recovery coefficient, and image uniformity. The energy windows were set to 350-650 keV on the MiniPET-2 and 360-662 keV on the MiniPET-3. RESULTS Spatial resolution was approximately 17% better on average for the MiniPET-3 than the MiniPET-2. The systems performed similarly in terms of peak absolute sensitivity (∼1.37%), spillover ratio for air (∼0.15), spillover ratio for water (∼0.25), and recovery coefficient (∼0.33, 0.59, 0.81, 0.89, and 0.94). Uniformity was 5.59% for the MiniPET-2 and 6.49% for the MiniPET-3. Minor differences were found in scatter fraction. With the ratlike phantom, the peak noise-equivalent counting rate was 14 kcps on the MiniPET-2 but 24 kcps on the MiniPET-3. However, with the mouselike phantom, these values were 55 and 91 kcps, respectively. The optimal coincidence time window was 6 ns for the MiniPET-2 and 8 ns for the MiniPET-3. CONCLUSION Images obtained with the SiPM-based MiniPET-3 small-animal PET system are similar in quality to those obtained with the conventional PMT-based MiniPET-2.

We report the results of a detailed study on the structural, electrical and optical properties of light emitting devices based on amorphous Si nanostructures. Amorphous nanostructures may constitute an interesting system for the monolithic integration of optical and electrical functions in Si ULSI technology. In fact, they exhibit an intense room temperature electroluminescence (EL), with the advantage of being formed at a temperature of 900 °C, while at least 1100 °C is needed for the formation of Si nanocrystals. Optical and electrical properties of amorphous Si nanocluster devices have been studied in the temperature range between 30 and 300 K. The EL is seen to have a bell-shaped trend as a function of temperature with a maximum at around 60 K. The efficiency of these devices is comparable to that found in devices based on Si nanocrystals, although amorphous nanostructures exhibit peculiar working conditions (very high current densities and low applied voltages). Time resolved EL measurements demonstrate the presence of a short lifetime, only partially due to the occurrence of non-radiative phenomena, since the very small amorphous clusters formed at 900 °C are characterized by a short radiative lifetime. By forcing a current through the device a phenomenon of charge trapping in the Si nanostructures has been observed. Trapped charges affect luminescence through an Auger-type non-radiative recombination of excitons. Indeed, it is shown that unbalanced injection of carriers (electrons versus holes) is one of the main processes limiting luminescence efficiency. These data will be reported and the advantages and limitations of this approach will be discussed. © 2006 IOP Publishing Ltd.

In this work we have studied the structural, electrical and optical properties of MOS devices, where the dielectric layer consists of a SiOx (x < 2) thin film prepared by plasma enhanced chemical vapor deposition and implanted with rare earth ions. As deposited SiOx films were annealed at high temperature (> 1000 degreesC) to induce the separation of the Si and SiO2 phases with the formation of Si nanocrystals embedded in the insulating matrix. Devices based on this system present a strong light emission at room temperature at a wavelength of about 900 nm. Devices emitting at different wavelengths have been fabricated by implanting SiOx films with Er or Tin. Devices based on Er-doped Si nanoclusters film exhibit an intense 1.54 mum room temperature electroluminescence (EL). We have calculated the excitation cross-section for Er ions in presence of Si nanoclusters under electrical pumping and the value is similar to1 x 10(-14) cm(2), comparable to the value found for the electrical excitation of undoped Si nanocrystals. Finally, devices based on Tm-doped Si nanoclusters exhibit two EL peaks at 0.78 and 1.7 mum.

Design and fabrication of single photon avalanche detector (SPAD) in planar technology is reported. Device design and critical issues in the technology are discussed. Experimental test procedures are described for dark-counting rate, afterpulsing probability, photon timing resolution, and quantum detection efficiency. Low-noise detectors are obtained, with dark counting rates down to 10 c/s for devices with 10 /spl mu/m diameter, down to 1 kc/s for 50 /spl mu/m diameter. The technology is suitable for monolithic integration of SPAD detectors and associated circuits.

Silicon photomultipliers (SiPMs) consist in arrays of tiny, passive quenched avalanche photodiode microcells working in Geiger mode and connected in parallel via integrated resistors. Novel types of SiPMs are being developed at STMicroelectronics (Catania, Italy) in n-on-p and p-on-n junction configurations optimized for visible-near infrared and blue-near ultraviolet light detection, respectively. All the tested devices show interesting performances in terms of high photon detection efficiency, low level dark rate, fast timing response and very good single photoelectron resolution also for high overvoltage values, confirming the excellent single photon detection capability of ST SiPM technology.

Silicon Photomultipliers (SiPMs) are fabricated in two different configurations: p-on-n and n-on-p junctions. More particularly p-on-n SiPMs turn out to be more suitable in nuclear medical imaging applications like Positron Emission Tomography (PET), due to their higher sensitivity in blue wavelength range where common PET scintillators have their emission spectrum. Here we report on the preliminary results of the electro-optical characterization performed on the first STMicroelectronics p-on-n SiPMs with standard (45%) and enhanced (62%) fill factor. The performances of these devices are compared with standard n-on-p technology. The inversion of the junction results in a remarkable improvement of PDE in blue wavelength range. Moreover all the tested devices show very good single photoelectron resolution also for high overvoltage values confirming the excellent single photon detection capability of SiPM technology. In this work a comprehensive SiPM model integrating the electrical and statistical behavior of the device is also presented. We used a Monte Carlo model for statistical and a SPICE circuit model for the electrical behavior description of the SiPM.

We report the electrical and optical comparison, in continuous wave regime, of two novel classes of silicon photomultipliers (SiPMs) fabricated in planar technology on silicon P-type and N-type substrate respectively. Responsivity measurements have been performed with an incident optical power from tenths of picowatts to hundreds of nanowatts and on a broad spectrum, ranging from ultraviolet to near infrared (340-820 nm). For both classes of investigated SiPMs, responsivity shows flat response versus the optical incident power, when a preset overvoltage and wavelength is applied . More in detail, this linear behavior extends up to about 10 nW for lower overvoltages, while a shrink is observed when the reverse bias voltage increases. With regards to our responsivity measurements, carried out in the abovementioned spectral range, we have found a peak around 669 nm for the N-on-P and a peak at 417 nm for the P-on-N SiPM. A physical explanation of the all experimental results is also provided in the paper.

Silicon Photomultipliers (SiPMs) are fabricated in two different configurations: P-on-N and N-on-P junctions. More particularly P-on-N SiPMs are more suitable for application in Positron Emission Tomography (PET), due to their higher sensitivity in blue wavelength range where common PET scintillators have their emission spectrum. In this paper we will report on the electro-optical performances of the first P-on-N SiPMs manufactured at STMicroelectronics-Catania. The results obtained on these devices are compared with those measured on the standard N-on-P technology. We will show that the performances of the new devices are extremely promising in terms of higher photon detection efficiency in blue wavelength range and lower cross talk effects.

Silicon Photomultipliers (SiPMs) have known a fast development in recent years, due to their excellent single photon detection capability and very fast timing response. In this paper we present the results of the electro-optical characterization performed on the first STMicroelectronics P on N SiPMs prototypes properly designed for their possible application in Positron Emission Tomography (PET). We will show that the performances of the new devices are extremely promising in terms of high photon detection efficiency and fast timing response in blue wavelength range.

The aim of this paper is to investigate on a statistical basis at the wafer level the relationship existing among the dark currents of the single pixel compared to the whole Silicon Photomultiplier array. This is the first time to our knowledge that such a comparison is made, crucial to pass this new technology to the semiconductor manufacturing standards. In particular, emission microscopy measurements and current measurements allowed us to conclude that optical trenches strongly improve the device performances.

In this contribution we present the results of the first morphological and electro-optical characterization of Silicon Photomultipliers (SiPM) for nuclear medical imaging applications fabricated in standard silicon planar technology at the STMicroelectronics Catania R&D clean room facility. We have improved our previous Geiger Mode Avalanche Photodiodes (GMAP) technology in order to realize a photodetector with relevant features in terms of single-photoelectron resolution, timing and photon detection efficiency. The performances of our devices, investigated in several experimental conditions and here reported make ST-SiPM suitable in many applications like for example PET (Positron Emission Tomography). Keywords: single photon counting, positron emission tomography, silicon photomultiplier, single photon avalanche photodiode, quenching resistor. 1. INTRODUCTION Photon counting techniques have been developed over many years by exploiting the remarkable performances of photomultiplier tubes (PMT) and avalanche photodiodes (APD) [1]. In r ecent years, a new kind of planar semiconductor photodetector, called Silicon PhotoMultiplier (SiPM), has been developed to detect single optical photons as a possible alternative to PMT and APD. SiPM have many advantages in terms of very fast timing response, high gain at low bias voltage, small recovery time, high detection efficiency in all the visible range and single photon response. Low bias voltage, low power consumption, good temperature and voltage stability, insensitivity to magnetic fields, reliability, ruggedness, compactness, no excess light damage and long lif espan are other favorable characteristics of these devices [2]. Moreover the solid-state detector approach has the typical advantages of a planar process integration, therefore arrays with a large number of pixels working in Geiger Mode can be manufactured at low cost

We present the properties and potentialities of light emitting devices based on amorphous Si nanoclusters. Amorphous nanostructures may constitute an interesting alternative to Si nanocrystals for the monolithic integration of optical and electrical functions in Si technology. In fact, they exhibit an intense room temperature electroluminescence (EL). The EL properties of these devices have been studied as a function of current and of temperature. Moreover, to improve the extraction efficiency of the light, we have integrated the emitting system with a 2D photonic crystal structure opportunely fabricated by using conventional optical lithography to reduce the total internal reflection of the emitted light. The extraction efficiency in such devices increases by a factor of 4 at a resonance wavelength.

In this paper, we summarize the results of an extensive investigation on the properties of MOS-type light emitting devices based on silicon nanostructures. The performances of crystalline, amorphous and Er-doped Si nanostructures are presented and compared. We show that all devices are extremely stable and robust, resulting in an intense room temperature electroluminescence (EL) at around 900 nm or at 1.54 mu m. Amorphous nanostructures may constitute an interesting system for the monolithic integration of optical and electrical functions in Si ULSI technology. In fact, they exhibit an intense room temperature EL with the advantage to be formed at a temperature of only 900 degrees C, remarkably lower than the temperature needed for the formation of Si nanocrystals (1100 degrees C or higher). To improve the extraction of the light, we coupled the emitting system with a 2D photonic crystal structure properly fabricated with ULSI technology to reduce the total internal reflection of the emitted light. We demonstrate that the extraction efficiency is increased by a factor of 4. Finally, the light emission from devices based on Er-doped Si nanoclusters has been studied and in particular we have investigated the luminescence quenching processes limiting quantum efficiency in these devices. In fact the carrier injection, that determines the excitation of Er ions through electron-hole recombination, at the same time produces an efficient non-radiative Auger deexcitation with trapped carriers. These data are presented and the implications on the device performances discussed.

The luminescence-quenching processes limiting quantum efficiency in Er-doped silicon nanocluster light-emitting devices are investigated and identified. It is found that carrier injection, while needed to excite Er ions through electron-hole recombination, at the same time produces an efficient nonradiative Auger deexcitation with trapped carriers. This phenomenon is studied in detail and, on the basis of its understanding, we propose device structures in which sequential injection of electrons and holes can improve quantum efficiency by avoiding Auger processes. © 2006 The American Physical Society.

We report on enhanced light extraction from a light-emitting device based on amorphous silicon nanoclusters, suitable for very-large-scale integration, and operating at room temperature. Standard low-cost optical lithography is employed to fabricate a two-dimensional photonic crystal onto the device. We measured a vertical emission with the extracted radiation enhanced by over a factor of 4, without the aid of any buried reflector. These achievements demonstrate that a cost-effective exploitation of photonic crystals is indeed within the reach of semiconductor industry and open the way to a new generation of nanostructured silicon devices in which photonic and electronic functions are integrated together. © 2006 American Institute of Physics.

We have studied the electrical and optical properties of light emitting MOS devices based on Si nanostructures. In these devices the dielectric layer consists of a SiOx thin film prepared by plasma enhanced chemical vapor deposition. As-deposited SiOx films were annealed at high temperature to induce the separation of the Si and SiO2 phases with the formation of Si nanocrystals (nc) embedded in the insulating matrix. Devices based on Si nc present a strong light emission at room temperature at a wavelength of about 900 nm. Devices emitting at different wavelengths have been fabricated by implanting SiOx films with rare earth ions. Devices based on Er, Tm and Yb-doped Si nanoclusters exhibit an intense room temperature electroluminescence (EL) respectively at 1.54 μm, 0.78 μm and 0.98 μm. The EL properties of the devices have been optimized through the study of the structural properties of their active layers by means of the energy filtered transmission electron microscopy (EFTEM) technique. EFTEM has evidenced the presence of a relevant contribution of amorphous nanostructures, and has given a very reliable quantitative estimation of the size and density of the Si nanostructures, as well as of the concentration of Si atoms remaining dissolved in the matrix. In the case of RE-doped SiOx films, the role of amorphous nanostructures in sensitizing the RE luminescence has been clearly demonstrated. These results open the way to new interesting applications in optoelectronics, such as electrically driven optical amplifiers or light sources.

In this paper we report the results relative to the design and fabrication of Single Photon Avalanche Detectors (SPAD) operating at low voltage in planar technology. These silicon sensors consist of pn junctions that are able to remain quiescent above the breakdown voltage until a photon is absorbed in the depletion volume. This event is detected through an avalanche current pulse. Device design and critical issues in the technology are discussed. Experimental test procedures are then described for dark-counting rate, afterpulsing probability, photon timing resolution, quantum detection efficiency. Through these experimental setups we have measured the electrical and optical performances of different SPAD technology generations. The results from these measurements indicate that in order to obtain low-noise detectors it is necessary to introduce a local gettering process and to realize the diode cathode through in situ doped polysilicon deposition. With such technology low noise detectors with dark counting rates at room temperature down to 10c/s for devices with 10mm diameter, down to 1kc/s for 50mm diameter have been obtained. Noticeable results have been obtained also as far as time jitter and quantum detection efficiency are concerned. This technology is suitable for monolithic integration of SPAD detectors and associated circuits. Small arrays have already been designed and fabricated. Preliminary results indicate that good dark count rate uniformity over the different array pixels has already been obtained.

This is a progress report on preliminary test measurements aimed to evaluate the performance of new Single Photon Avalanche Diodes (SPAD) developed by ST Microelectronics. Various samples with different dimensions (from 10 to 100 μm diameter) and two 5x5 arrays (20 and 40 μm) are manufactured by STM; some of which have been characterized. A brief description of the device and its main characteristics (dark, quantum efficiency and linearity) are presented.

The electroluminescence (EL) properties of Er-doped Si nanoclusters (nc) embedded in metal-oxide-semiconductor devices are investigated. It is shown that, due to the presence of Si nc dispersed in the SiO2matrix, an efficient carrier injection occurs and Er is excited producing an intense 1.54 μm room temperature luminescence. The EL properties as a function of the current density, temperature and time have been studied in details, elucidating the radiative and non-radiative de-excitation properties of the system. We have also estimated the excitation cross section for Er under electrical pumping finding a value of −1×10 cm. This value is two orders of magnitude higher than the effective excitation cross section of Er ions through Si nc under optical pumping, and quantum efficiencies of ∼1% are obtained at room temperature in these devices. These data will be presented and the impact on future applications discussed.

We have fabricated MOS devices where the dielectric layer consists of a substoichiometric SiO x (x thin film , annealed at 1100°C for 1 h to induce the separation of the Si and SiO 2 phases, with the formation of silicon nanocrystals (nc) embedded in the insulating matrix. We have studied the electroluminescence (EL) properties of such devices as a function of the current density and of the temperature. We have evaluated the excitation cross section of Si nc under electrical pumping at room temperature and at low temperature (12 K ) . Moreover, we have used the experimental EL intensities and decay times to evaluate the radiative rate as a function of the temperature.

In this work, the stationary and time-resolved electroluminescence (EL) properties of Si quantum dots embedded within a metal–oxide–semiconductor device are investigated. In particular, we measured the excitation cross section of Si nanocrystals under electrical pumping, finding a value of 4.7×10−14 cm2 which is two orders of magnitude higher with respect to the excitation cross section under 488 nm optical pumping. We also studied the radiative and nonradiative decay processes occurring in these devices by measuring the time evolution of the EL signal. We demonstrate that the mechanism responsible for the emission is the same under both electrical and optical pumping. The overall quantum efficiency of the electrical pumping is estimated to be two orders of magnitude higher than the quantum efficiency for optical pumping in all the studied temperature ranges.

The electroluminescence (EL) properties of Er-doped Si nanoclusters (NC) embedded in metal-oxide-semiconductor devices are investigated. Due to the presence of Si NC dispersed in the SiO2 matrix, an efficient carrier injection occurs and Er is excited, producing an intense 1.54 mum room temperature EL. The EL properties as a function of the current density, temperature, and time have been studied in detail. We have also estimated the excitation cross section for Er under electrical pumping, finding a value of similar to1x10(-14) cm(2). This value is two orders of magnitude higher than the effective excitation cross section of Er ions through Si NC under optical pumping. In fact, quantum efficiencies of similar to1% are obtained at room temperature in these devices.

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We have studied the structural, optical and electrical properties of MOS devices, where the dielectric layer consists of a substoichiometric SiOx (x < 2) thin film deposited by plasma enhanced chemical vapor deposition. After deposition the SiOx samples were annealed at high temperature (> 1000°C) to induce the separation of the Si and SiO2 phases with the formation of Si nanocrystals embedded in the insulating matrix. The effects of the Si concentration in the SiOx layer and of the annealing temperature on the electrical and optical properties of these devices are reported and discussed. It is shown that by increasing the Si content in the SiOx layers the operating voltage of the device decreases and the total efficiency of emission increases. In fact, devices having an active layer with high Si concentration (46 at.%) annealed at 1100 °C, exhibit the best performances (i.e. the highest electroluminescence intensity and the lowest operating voltage). Furthermore, we have observed that by decreasing the thickness of the SiOx layer from 75 to 25 nm it is possible to strongly reduce the operating voltage down to 4 V.