G. Fallica

Silicon Photomultiplier Technology at STMicroelectronics

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).

Timing Performances of Large Area Silicon Photomultipliers Fabricated at STMicroelectronics

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.

A monolithic silicon detector telescope

Abstract An ultrathin silicon detector (1 μm) thick implanted on a standard 400 μm Si-detector has been built to realize a monolithic telescope detector for simultaneous charge and energy determination of charged particles. The performances of the telescope have been tested using standard alpha sources and fragments emitted in nuclear reactions with different projectile-target colliding systems. An excellent charge resolution has been obtained for low energy (less than 5 MeV) light nuclei. A multi-array lay-out of such detectors is under construction to charge identify the particles emitted in reactions induced by low energy radioactive beams.

Quantum Detection Efficiency in Geiger Mode Avalanche Photodiodes

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.

Crosstalk Characterization in Geiger-Mode Avalanche Photodiode Arrays

Following our work on Geiger-mode avalanche photodiode arrays, we have recently been dealing with the crosstalk issue in newly developed dense arrays with a minimum distance between pixel centers of 84 mum. In this paper, we present our crosstalk measurement approach, including the experimental setup and the offline calculation methods. Different characterizations of the crosstalk probability PCT versus capacitance have been performed to extrapolate the PCT when no measurement setup loads the pixels. We also present results regarding the crosstalk probability versus pixel distance and bias. Moreover, by adopting a slightly different approach, the probability density decay time has been measured to investigate about crosstalk origin.

Measurements of Silicon Photomultipliers Responsivity in Continuous Wave Regime

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.

Electro-Optical Performances of p-on-n and n-on-p Silicon Photomultipliers

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.

A large area cosmic ray detector for the inspection of hidden high-Z materials inside containers

Traditional inspection methods are of limited use to detect the presence of fissile (U, Pu) samples inside containers. To overcome such limitations, prototypes of detection systems based on cosmic muon scattering from high-Z materials are being tested worldwide. This technique does not introduce additional radiation levels, and each event contributes to the tomographic image, since the scattering process is sensitive to the charge of the atomic nuclei being traversed. A new Project, started by the Muon Portal Collaboration, plans to build a large area muon detector able to reconstruct muon tracks with good spatial and angular resolution. Experimental tests of the individual detection modules are already in progress. The design and operational parameters of the muon portal under construction are here described, together with the preliminary simulation and test results. Due to the large acceptance of the detector for cosmic rays, coupled to the good angular reconstruction of the muon tracks, it is also planned to employ such detector for cosmic ray studies, complementing its detection capabilities with a set of trigger detectors located some distance apart, in order to measure multiple muon events associated to extensive air showers.

SPAD arrays and micro-optics: towards a real single photon spectrometer

This study aims at proving that single photon sensing can be made accessible in the form of cheap off-the-shelf micro-devices with micro-optical/micro-mechanical coupling systems. In order to achieve this challenging goal, use is made of different micro-technologies, not yet fully established but promising and innovative in and of themselves. It is planned to combine them into a more challenging micro-technology capable of making single photon handling off-the-shelf. Moreover, the technology to be implemented should make it possible to provide photonic sensors in a ready-to-go fashion.

Silicon Photomultipliers for nuclear medical imaging applications

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).