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This paper presents a sub-mW ASIC for multimodal brain monitoring. The ASIC is co-integrated with electrode(s) and optodes (i.e., optical source and detector) as an active sensor to measure electroencephalography (EEG), bio-impedance (BioZ), and near-infrared spectroscopy (NIRS) on scalp. The target is to build a wearable EEG-NIRS headset for low-cost functional brain imaging. The proposed NIRS readout utilizes the near-infrared light to measure the pulse oximetry and blood oxygen saturation (SpO2). While traditional photodiodes are supported, the readout also allows the use of silicon photomultipliers (SiPMs) as optical detectors. The SiPM improves optical sensitivity while significantly reducing the average power of two LEDs to 150 μW. On circuit level, a SAR-based calibration compensates maximum 40 μA current from ambient light, while digital DC-servo loops reduces the baseline static SiPM current up to 400 μA, leading to an overall dynamic range of 87 dB. The EEG readout exhibits 720 MΩ input impedance at 50 Hz. The BioZ readout has 3 mΩ/√(Hz) impedance sensitivity by employing dynamic circuit techniques. When EEG, BioZ, and NIRS are enabled at the same time, one ASIC consumes 665 μW including the power of LEDs. [ABSTRACT FROM AUTHOR]

There is an increasing interest to use silicon photomultipliers (SiPMs) in medical applications like Photoplethysmography or Functional Near Infrared Spectroscopy, allowing the monitoring of physiological signs through non-invasive equipment. The use of large area SiPMs with embedded color filters for environmental light rejection could bring relevant advantages in these applications in terms of higher signal-to-noise ratio of the measurements. Here, we report on the first electro-optical characterization results obtained on n-on-p SiPMs with green interference bandpass filters glued on the top side of the detector SMD package. We will show how the use of the filter considerably increases, especially for large overvoltage values, the SiPM dark noise rate, due to the significant amplification of optical cross-talk effects (up to 150% of dark current increase at 50%-OV). This makes necessary a careful evaluation of the SiPMs performances in order to define the best operating conditions and layout characteristics of the detectors that will be used in the final applications. [ABSTRACT FROM PUBLISHER]

A silicon carbide (SiC) detector was calibrated in terms of quantum efficiency (QE) as well as its spectral responsivity at two different wavelength radiations ( \lambda N2 = 2.88 nm and \lambda Ne= 1.35 nm), using two different calibrated Si detectors, sensitive to the soft X-ray radiation ( $\lambda = 0.1\div 10$ nm). An Nd:YAG laser was employed to irradiate a nitrogen and a neon gas-puff target, producing a plasma, which is emitting radiation used for estimation of the detector parameters. A possibility to characterize a new generation of not commercial SiC detectors, with a higher band gap with respect to Si, employing a gas-puff target source, will be presented. Measurements show the SiC detectors QE, equal to 3.4 and 7.1 e/ph for 2.88- and 1.35-nm wavelength radiations, respectively. Calculations and results are reported and discussed. [ABSTRACT FROM AUTHOR]

In this paper, we propose a UV-A sensor based on a 6H-SiC Schottky photodiode with a thin Ni2Si front electrode and an integrated hydrogenated silicon nitride (SiN:H) dielectric filter. 6H-SiC prototypes were fabricated by using a manufacturing process to a large extent already implemented on 4H-SiC poly-type for the realization of a high signal-to-noise ratio ultraviolet (UV) sensor already commercialized. The results obtained on 6H-SiC prototypes show optimal electrical performance with dark current density lower than 0.2 nA/cm2 at room temperature and 10 V reverse bias. The use of 6H polytype allows shifting of the UV sensor response from 290 nm peak responsivity wavelength measured on standard 4H-SiC photodiodes to 360 nm wavelength in 6H-SiC prototypes with an integrated SiN:H filter exactly in the middle of the UV-A band (320–400 nm) with a simultaneous consistent reduction of the optical response in UV-C and UV-B regions below 320 nm wavelength. [ABSTRACT FROM PUBLISHER]

The use of healthcare sensors in portable and wearable devices has drawn increasing attention in the last few months. More particularly, the integration of ultraviolet (UV) light sensors to monitor UV sunlight radiation in next generation smartphones has been widely discussed recently. Here, we propose 4H-SiC Schottky photodiodes with three different geometries suitably designed to operate in photovoltaic condition for UV light monitoring. The electrical and optical characteristics of these devices are investigated as a function of the bias and temperature applied to the detectors. [ABSTRACT FROM PUBLISHER]

Photodetection in the ultraviolet (UV) region has drawn extensive attention owing to its various applications in industrial, environmental, and even biological fields. In this letter, we report on the morphological and electro-optical characteristics of continuous thin metal film Ni2Si/4H-SiC photodiodes properly designed for the realization of an extremely compact digital sensor suited to measure the total sun UV radiation for environmental UV light monitoring. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM AUTHOR]

There is significant scientific evidence demonstrating that excessive exposure to ultraviolet (UV) radiation in sunlight and from artificial sources may cause acute and chronic adverse health effects to skin and eye. The Global Solar UV Index (UVI) describes the level of solar UV radiation at the Earth's surface. The higher the index value, the greater the potential for damage to the skin and eye, and the less time it takes for harm to occur. In this letter, we report on a demonstrator board suitably designed for UVI monitoring using visible blind high signal-to-noise ratio 4H-SiC Schottky photodiodes as UV light detectors. [ABSTRACT FROM PUBLISHER]

New equations for paralyzable, non paralyzable and hybrid DT models, valid for any time dependent sources are presented. We show how such new equations include the equations already used for constant rate sources, and how it's is possible to correct DT losses in the case of time dependent sources. Montecarlo simulations were performed to compare the equations behavior with the three DT models. Excellent accordance between equations predictions and Montecarlo simulation was found. We also obtain good results in the experimental validation of the new hybrid DT equation. Passive quenched SPAD device was chosen as a device affected by hybrid DT losses and active quenched SPAD with 50 ns DT was used as DT losses free device. [ABSTRACT FROM AUTHOR]

In this paper the results of charge and timing resolution characterization realized at Fermi National Accelerator Laboratory (Fermilab) on 3.5 \times 3.5~mm^2 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. [ABSTRACT FROM PUBLISHER]

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). [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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[sup+] - P and P[sup+] - N junctions is given. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]