Solid-state Photomultiplier Research Articles

Recent developments with CMOS SSPM photodetectors

Experiments and simulations using various solid-state photomultiplier (SSPM) designs have been performed to evaluate pixel layouts and explore design choices. SPICE simulations of a design for position-sensing SSPMs showed charge division in the resistor network, and anticipated timing performance of the device. The simulation results predict good position information for resistances in the range of 1–5 kΩ and 150-Ω preamplifier input impedance. Back-thinning of CMOS devices can possibly increase the fill factor to 100%, improve spectral sensitivity, and allow for the deposition of anti-reflective coatings after fabrication. We report initial results from back illuminating a CMOS SSPM, and single Geiger-mode avalanche photodiode (GPD) pixels, thinned to 50 μm.

SSPM Readout of LSO, (Lu-Y)AP:Ce and PWO-II Pixels for PET Detector Modules

We have studied the performance of recently developed solid state photomultipliers (SSPMs) with 2.1times2.1 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> sensitive area as a readout for small LSO, (Lu-Y)AP:Ce and PWO-II scintillator crystals. The SSPM is based on the p <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> -p-n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> structure which was optimized for blue/UV light detection. It operates at a gain of >10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> and shows >25% photon detection efficiency in the 380-600 nm spectral range. Energy and timing spectra were measured using a <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">22</sup> Na gamma source. Energy resolutions of 13%, 25% and 50% FWHM were measured for 511 keV gammas with the LSO, (Lu-Y)AP:Ce and PWO-II scintillator crystals respectively. A coincidence timing resolution of 710 ps (FWHM) was measured between two identical LSO+SSPM modules.

An Investigation Into the Use of Geiger-Mode Solid-State Photomultipliers for Simultaneous PET and MRI Acquisition

Photon detecting Geiger-mode solid-state devices are being actively researched and developed because, unlike photo- multiplier tubes (PMT), they can be used in high-magnetic-field and radio-frequency environments, such as in magnetic resonance imaging (MRI) scanners. In addition, some Geiger-mode solid-state devices have higher photon detection efficiencies than PMTs and higher gains than avalanche photo-diodes (APD). We tested Geiger-mode solid-state photomultipliers (SSPM) inside a 3 T MRI to study the possibility of using them in combined PET/MRI scanners. Approximately 16% energy resolutions and ~1.3 ns coincidence time resolutions with 22Na and lutetium yttrium oxyorthosilicate (LYSO) were obtained for full-width at half maximum (FWHM) for T1, T2, and gradient echo T2* MRI pulse sequences with little MR image degradation. The study shows that SSPMs have excellent potential for use in combined PET/MRI scanners.

A scintillation γ-ray detector based on a solid-state photomultiplier

A scintillation detector based on a silicon photodetector of a new type—a solid-state photomultiplier—and a single-crystal CsI(Tl) scintillator was investigated. The effect of temperature on the low-energy detection threshold and the energy resolution of the detector and the influence of the radiation level on the detector efficiency (i.e., the influence of the counting rate of the distortion in the recorded spectrum shape) were estimated. A mathematical model of the detector was developed in order to assess its parameters.

Initial experimental studies of using solid-state photomultiplier for PET applications

An evaluation of solid-state photomultiplier (SSPM) has been conducted for Positron Emission Tomography (PET) applications. The single-channel PET detector has been measured for its performance with respect to linearity of light detection, energy resolution, coincidence timing resolution, and depth-of-interaction detection capability. The SSPMs used have a 1×1 mm 2 active detection area. At nominal bias, it has a peak sensitivity around 470 nm, typical single photon detection efficiency around 20%, gain about 600,000, dark current 25 μA, and excess noise factor <1.3. A trans-impedance preamplifier was used to read the signal under operating conditions consisted with a balanced energy and timing performance for the PET application. In this initial study, there was a geometry mismatch between the SSPM and LSO crystal with a 2×2 mm 2 cross-sectional area, where the light loss could reach 75%. Measured energy and coincidence timing resolutions are 23% and 1.8 ns, respectively, all within the SSPM linear region of photon detection up to ∼250 photoelectrons. The depth-of-interaction (DOI) resolution was measured with two SSPMs detecting lights at both ends of a 1.8×2×20 mm 3 LSO crystal, using a conventional electronic collimation method to localize the DOI positions. The measured DOI resolution was 4.5 (+/−0.3) mm, sufficient to develop a PET detector for the measurement of 3D interaction locations. These preliminary measurements have demonstrated the feasibility of using SSPMs for PET applications.

Investigation of Solid-State Photomultipliers for Positron Emission Tomography Scanners

Solid-state devices to detect photons are under active research and development because they, unlike photomultiplier tubes (PMT), can be used under high-magnetic-field and radio-frequency environments, such as in magnetic resonance imaging (MRI) scanners. In addition, some of the solid-state devices have a higher particle detection efficiency and only a slightly less gain than PMTs, currently the first choice to detect photons in positron emission tomography (PET) scanners. We have tested solid-state photomultipliers (SSPM) among several different solid-state devices in the market. This paper describes the test methods and the characteristics of SSPMs with an emphasis on use in PET scanners. We obtained a 25 % energy resolution and a 4.5-ns time resolution with Na and lutetium yttrium oxyorthosilicate (LYSO), both full-width at half maximum (FWHM). The number of fired mini-cells and the amplification factor were, respectively, estimated to be 154 ± 37 for Na and (3.8 ± 0.9) × 10. Even though SSPM-LYSO couplings resulted in worse performances than PMT-LYSO couplings, the solid-state devices have good potential for use in the PET scanners, especially in combined PET/MRI scanners because the new solid-state devices appear to have better characteristics, such as a higher quantum efficiency and a larger number of mini-cells, than the tested SSPMs.

Direct photon-counting scintillation detector readout using an SSPM

Gamma-ray detector technologies, capable of providing adequate energy information, use photomultiplier tubes (PMTs) or silicon avalanche photodiodes to detect the light pulse from a scintillation crystal. A new approach to detect the light from scintillation materials is to use an array of small photon counting detectors, or a “detector-on-a-chip” based on a novel “Solid-state Photomultiplier” (SSPM) concept. A CMOS SSPM coupled to a scintillation crystal uses an array of CMOS Geiger photodiode (GPD) pixels to collect light and produce a signal proportional to the energy of the radiation. Each pixel acts as a binary photon detector, but the summed output is an analog representation of the total photon intensity. We have successfully fabricated arrays of GPD pixels in a CMOS environment, which makes possible the production of miniaturized arrays integrated with the detector electronics in a small silicon chip. This detector technology allows for a substantial cost reduction while preserving the energy resolution needed for radiological measurements. In this work, we compare designs for the SSPM detector. One pixel design achieves maximum detection efficiency (DE) for 632-nm photons approaching 30% with a room temperature dark count rate (DCR) of less than 1 kHz for a 30-μm-diameter pixel. We characterize after pulsing and optical cross talk and discuss their effects on the performance of the SSPM. For 30-μm diameter, passively quenched CMOS GPD pixels, modeling suggests that a pixel spacing of approximately 90 μm optimizes the SSPM performance with respect to DE and cross talk.

Characterization and scintillation studies of a solid-state photomultiplier

The solid-state photomultiplier (SSPM) is a relatively new semiconductor based photodetector that, by using hundreds of micro silicon Geiger APDs, possesses high gain ( 10 5 – 10 6 ) and low noise while needing only low voltage (40–60 V) to operate. The fast response and high intrinsic gain of SSPMs makes them attractive for timing applications, in particular for positron emission tomography (PET). Here we present the results from the characterization of a 1 × 1 mm 2 SSPM (SSPM-050701GR-TO18, Photonique SA). Several intrinsic SSPM characteristics were measured such as gain, dark noise, and linearity. Single photon spectra were also collected. Additionally, scintillation studies were performed. The SSPM was coupled to CsI:Tl and LSO scintillation crystals and exposed to various common laboratory radionuclides to measure photopeak energy resolutions. The linearity of the SSPM, when coupled with a scintillator, was also measured. Using a 22Na source (511 keV annihilation photons) and LSO, the SSPM FWHM energy resolution is 14.4 % ± 0.2 % and the estimated coincidence FWHM timing resolution is 0.84 ns ± 0.02 ns .

Test of scintillator readout with single photon avalanche photodiodes

We outline the possible applications of newly developed single photon avalanche detectors (SPAD) operating at low voltage and fabricated in silicon planar technology, reporting on tests done with scintillators. We envisage the integration of large arrays of identical sensors, employing a common read-out mode in order to achieve a high resolution and high sensitivity solid state photomultiplier. The applications of such a device would be many, particularly if we consider that we are also working on the production of microoptical components, perfectly suited for the lossless coupling of these photosensors to several light sources (lasers, ordinary and scintillating fibers, scintillators, optical devices), by exploiting the promising deep lithography with ions (DLI) technology. Crossed time-of-flight and charge measurements between SPADs and usual photomultipliers, coupled to scintillators, have allowed to compare their relative performance. Specific issues regarding the SPAD and the scintillating fiber readout are presented, also in view of possible applications in the field of particle/radiation tracking systems

The recent development and study of silicon photomultiplier

Recent developments and results from the study of a Silicon Solid State Photomultiplier (Si-PM) are presented. The basis of this new type of photodetector is a fine structure of microcells operating in the Geiger mode with an internal gain greater than 106. Common signal output allows for the detector to be operated in the proportional mode, and to reach a dynamic range of 1.5×103. Such photodetectors have shown single photon response at room temperature with a fast timing of ∼100 ps. They are compact, robust and non-sensitive to magnetic fields. Results show the detection of low-intensity light in single photon mode and the detection of minimal ionizing particles using a scintillation tile for hadron calorimetry. The silicon photomultiplier is suitable for wide application in scintillation calorimetry, medical application, etc.

The recent development and study of silicon photomultiplier

Recent developments and results from the study of a Silicon Solid State Photomultiplier (Si-PM) are presented. The basis of this new type of photodetector is a fine structure of microcells operating in the Geiger mode with an internal gain greater than 10 6 . Common signal output allows for the detector to be operated in the proportional mode, and to reach a dynamic range of 1.5 × 10 3 . Such photodetectors have shown single photon response at room temperature with a fast timing of ∼ 100 ps. They are compact, robust and non-sensitive to magnetic fields. Results show the detection of low-intensity light in single photon mode and the detection of minimal ionizing particles using a scintillation tile for hadron calorimetry. The silicon photomultiplier is suitable for wide application in scintillation calorimetry, medical application, etc.

Single-photon turnstile device: simultaneous Coulomb blockade for electrons and holes

Utilizing simultaneous Coulomb blockade for electrons and holes in a p-n junction, we can realize a device where a single electron and a single hole are injected into the active region to produce a single photon with well-regulated time interval. The photons emitted from such a device can be studied with single photon counting detectors using a Si solid-state photomultiplier. We report locking of the photon emission with external driving pulse, in the regime where one electron and one hole are injected into the active region on the average.

Measurement of the rate capability of solid state photomultipliers using visible light

The rate capability of solid state photomultipliers has been studied for various combinations of temperature and bias voltage. Using a 635 nm laser diode flasher measurements were made up to a single photoelectron rate of 12MHz. Only a slight decrease, less than several per cent, of the quantum efficiency was observed at this rate whereas a 10% drop of the gain was observed.

Noise-free avalanche multiplication in Si solid state photomultipliers

Si solid state photomultipliers utilize impact ionization of shallow impurity donor levels to create an avalanche multiplication when triggered by a photoexcited hole. The distribution of pulse height from a single photon detection event shows narrow dispersion, which implies that the avalanche multiplication process in these devices is inherently noise-free. We have measured the excess noise factor using two different techniques, digital pulse height analysis and analog noise power measurement. The results demonstrate nearly noise-free avalanche multiplication accomplished in these devices.

High Time Resolution Infrared Observations of the Crab Nebula Pulsar and the Pulsar Emission Mechanism

We present new, high signal-to-noise near-infrared observations of the Crab Nebula pulsar using the Solid State Photomultiplier instrument on the Multiple Mirror Telescope. Our observations cover the J (1.25 μm), H (1.65 μm), and K (2.2 μm) infrared wavebands and have 20 μs time resolution. Together with visible and UV observations made by the Hubble Space Telescope High-Speed Photometer, we have high time resolution observations covering over a decade in wavelength. We present the pulse profiles over this wavelength range, and we analyze the pulse shape as a function of wavelength, including the peak-to-peak phase separation, the peak full width half-maxima (FWHM), and the peak half-width half-maxima (HWHM). We also create both phase-averaged and phase-resolved color spectra of the pulsar emission. We find that the peak-to-peak phase separation shows a significant trend for an increase with wavelength, in rough agreement with models of the pulsar emission mechanism. The FWHM for peaks 1 and 2 also show a trend for increase with wavelength, again in qualitative agreement with the models. However, the HWHM for peaks 1 and 2 show significant differences in their wavelength dependences from the leading to trailing edges. This behavior is not predicted by current pulsar emission models, and the different wavelength dependences of the component HWHM values call into question the usefulness of FWHM measurements. Our spectral analyses show that the IR-UV dereddened phase-averaged color spectrum is essentially flat over more than a decade in frequency. This is in clear contrast to the X-ray and γ-ray regimes, where the spectrum is falling steeply. The color spectra of peaks 1 and 2 are also essentially flat, but the ratio of the two shows statistically significant variations from a constant value. Finally, the color spectra of peaks 1 and 2 show significant differences from the leading to trailing edges. As with the HWHM, this behavior is not predicted by current pulsar emission models.

AN SSPM-BASED HIGH-SPEED NEAR-INFRARED PHOTOMETER FOR ASTRONOMY

ABSTRACT We describe the design, operation, and performance of a new high-speed infrared photometer using the Solid-State Photomultiplier (SSPM) detector. The SSPM was developed by Rockwell International Science Center and has single-photon counting capability over the 0.4-28 micron wavelength range, intrinsic time rsponse of order 1 ns, and low detector noise (Petroff, et al. 1987). We have operated a 200x200-micron back-illuminated SSPM in a liquid-helium cooled dewar with a room-temperature transimpedance amplifier output. Single photon pulses can be easily distinguished above the amplifier noise The individual photon pulses are binned at a selectable time resolution ranging from 5 microns to 64 ms, and then written to Exabyte tape. In the first astronomical application of such a device, we have made observations of the Crab Nebula pulsar and Her X-1 at near-infrared wavelengths (J-, H-, and K-bands), and we present the instrument sensitivities established by these observations. We discuss other astronomical observations which are either planned or currently underway. Finally, we present design specifications and predicted performances for a second-generation SSPM high-speed infrared photometer.

Feasibility of 1.5 µm staircase solid state photomultipliers in the AlGaSb/GaInAsSb system

We report the growth of a staircase solid state photomultiplier structure. The device is obtained by a combination of ternary AlGaSb and quaternary GaInAsSb graded layers epitaxied on GaSb substrates, using molecular beam epitaxy. The different layers used in the structures have been individually optimized for their electrical and optical quality. A multiplication coefficient of 7, without excess noise, is estimated on a six-step device, for a maximum voltage of only 15 V.

Detection of S 2 chemiluminescence in solid Ar using a solid-state photomultiplier

We have developed a spectrometric system based on a single-photon counting solid-state photomultiplier (SSPM). The SSPM can count single photons from the visible (400 nm) into the infrared (28 μm) with a high quantum yield. We have used the visible photon counting abilities in order to develop proper amplification, electronics circuitry and optical methods for the SSPM, so that we may apply them to infrared studies in the future. Here we present a test study; we have recorded the B″ 3Π u→X 3Σ g − transitions of S 2, created from the reactions of sulfur atoms in solid argon.

Atomically abrupt semiconductor heterointerfaces: their role in advanced electronic and photonic devices and quantum phenomena

Atomically abrupt heterojunction interfaces have played a unique role in the emergence of a new generation of electronic and photonic devices. These include quantum-well lasers, low-noise superlattice avalanche photodiodes and solid-state photomultipliers, quantum-well infrared photodetectors, ultrahigh-speed heterojunction bipolar transistors and resonant-tunneling devices. The monolayer abruptness of heterojunction interfaces has also made possible the observation of exciting quantum phenomena including resonant tunneling, giant nonlinear susceptibilities associated with the quantum size effect and electron Bragg reflection phenomena. The latter have been observed in transport and in the creation of new bound states at energies in the classical continuum above potential wells. A brief discussion of recent work on tunable band discontinuities concludes this paper.

A Long-Wavelength Infrared Photoluminescence Spectrometer for the Characterization of Semiconductor Materials

AbstractA new photoluminescence spectrometer has been developed for the characterization of optical emission in the 2.5 to 14.1 micron wavelength range. This instrument provides high sensitivity for the detection of interband and defect luminescence in a variety of infrared detector materials. The spectrometer utilizes a solid state photomultiplier detector and a circular variable filter, which serves as the resolving element. The entire spectrometer is cooled to 5K in order to decrease thermal radiation emission. Band-edge luminescence at 10.1 microns from HgCdTe samples has been readily detected with argon-ion laser excitation powers less than 70 mW/cm2. Representative spectra from HgCdTe and other infrared detector materials are presented.