Geiger-mode ladar cameras

Single-photon detector (SPD) as an essential building block for detecting and counting photons, plays a fundamental role in quantum technologies. In this work, we propose an efficient workflow of modeling SPDs based on emerging one-dimensional materials, i.e. nanowires, utilizing avalanche breakdown in reverse biased condition. Comparing to another extensively studied platform, superconducting nanowire SPDs, avalanche nanowire device is demonstrated in this work to promise comparable performance (e.g. high photon detection efficiency (PDE) and and low dark count rate (DCR)) but without working at extreme cryogenic temperature (4K). The proposed workflow explored to maximize computational workload and balancing between time-consuming drift-diffusion simulation and fast script-based post-processing, and in timely convergence we were able to predict a suite of key performance metrics for single-photon SPDs, including breakdown voltage, PDE, DCR, and time resolution.

The Multi-Pixel Photon Counter (MPPC) is a Geiger-mode avalanche photo-diode (APD) developed by Hamamatsu Corp. We propose that it could be a suitable photo-sensor for next-generation time-of-flight PET detectors due to its high photon detection efficiency. We concentrate on the measurement of coincidence timing performance of various MPPCs in conjunction with LYSO crystal scintillators. With 3 mm times 3 mm devices of 50 mum sub-pixels coupled to 3 mm times 3 mm times 10 mm LYSO crystals, we have demonstrated a strong dependence of timing performance on over-voltage and temperature, and analyzed how changes in photon detection efficiency and dark counts would explain the measurements. The best coincidence timing resolution we have achieved between two identical LYSO/MPPC detectors was 240 ps in FWHM. This was worse than the timing resolution of 220 ps obtained with a Hamamatsu H6533 fast PMT, and contradicted the expected improvement from higher photon detection efficiency. The contradiction could be explained by the slow rise-time of MPPC pulse shape, transit time spread, dark counts and electronic noise from the large capacitance of the MPPC. In particular, the slow rise-time of the MPPC pulse suggests the need for a very low trigger threshold on the timing circuit. Since this makes the detector system more sensitive to noise, this poses additional challenges for ganging multiple devices together into a commercially viable time-of-flight PET block detector. We will discuss this work in detail including other challenge imposed by MPPC characteristics.

As the core device of quantum information field, single photon avalanche photodiode (SPAD) is a solid-state single photon detector with pico-second level time-resolution, low bias voltage, high signal-to-noise ratio and low cost. However, the photon detection efficiency (PDE) of SPAD is not ideal. Traditional method is to optimize the device structure, and the dark count or time resolution characteristics of the device might be sacrificed. The metasurface integrated on SPADs provides a novel approach to achieve higher PDE. As a result, the SPAD device structure could be independently designed to realize low dark count rate and good time resolution. In this paper, many kinds of metasurface structures that could enhance the incident photons absorption, are analyzed. Those structures compatible with CMOS or other easy to mass produce processes are attractive to be adopted to make revolutionary changes to conventional SPAD. As a results, the metasurface integrated SPAD would strongly push its applications in the quantum information, single photons imaging, life medicine, and other low level light detections.

PureB single-photon avalanche diodes (SPADs) were investigated with the aid of a newly developed TCAD-based numerical modeling method with which characteristics related to the avalanching behavior can be simulated. The p + region forming the anode of the PureB p + n photodiode is extremely shallow, only a few nanometer deep, which is essential for obtaining a high photon detection efficiency (PDE) for near-, vacuum- and extreme-ultraviolet (NUV/VUV/EUV) light detection but when an implicit guard ring (GR) is implemented, the dark count rate (DCR) can, despite the GR, be deteriorated at the very sharp corners of the p + -region where there is a high concentration of the electric-field. By comparing measurements to simulations, the main mechanism dominating the DCR in the PureB SPADs was identified as band-to-band tunneling (BTBT) while trap-assisted-tunneling also plays a role when the perimeter breakdown is low. Increasing the dose of carriers in the enhancement region negatively impacts the total DCR of the device, but also shifts the origin of the dominant DCR contribution from perimeter to the active region. The simulations for optimization of the SPAD geometry predict that a modification of the n-doped epitaxial region of the PureB SPADs could decrease the DCR by almost two orders of magnitude. This is achieved by increasing the n-epi-layer thickness from 1 μm to 3 μm and lowering the doping from 10 15 cm -3 to 10 14 cm -3. A high electric field at the vertical pn junction in the active region can also be minimized by modifying the implantation parameters of the n-enhancement region thus keeping the BTBT contribution to the DCR sufficiently low.

TID effect induced degradation of IRFPA ROIC in cryogenic temperature

We developed the novel photon counter, named multipixel photon counter (MPPC). It is solid state photon counter using Geiger-mode APD and self-quenching resistance. It has many features like low bias voltage operation, high gain and insensitive to magnetic fields. We have fabricated the three kinds of MPPC, which are 40 times 40, 20 times 20, and 10 times 10 pixels segmented from 1 mm times 1 mm total active area. The gain, dark count rate, photon detection efficiency (PDE) and time resolution are measured and confirmed that MPPC has large potential as the new photon detection device.

In this paper, we describe the design, characterization, and modeling of InGaAsP/InP avalanche diodes designed for single photon detection at wavelengths of 1.55 and 1.06 mum. Through experimental and theoretical work, we investigate critical performance parameters of these single photon avalanche diodes (SPADs), including dark count rate (DCR), photon detection efficiency (PDE), and afterpulsing. The models developed for the simulation of device performance provide good agreement with experimental results for all parameters studied. For 1.55-mum SPADs, we report the relationship between DCR and PDE for gated mode operation under a variety of operating conditions. We also describe in detail the dependence of afterpulsing effects on numerous operating conditions, and in particular, we demonstrate and explain a universal functional form that describes the dependence of DCR on hold-off time at any temperature. For 1.06-mum SPADs, we present the experimentally determined relationship between DCR and detection efficiency for free-running operation, as well as simulations complementing the experimental data.

In the last years many progresses have been made in the field of Silicon Single Photon Avalanche Diodes (SPAD) thanks to the improvements both in device design and in fabrication technology. For example, the use of custom fabrication processes has allowed a steadily improvement of SPAD performance in terms of active area diameter, Dark Count Rate (DCR), and Photon Detection Efficiency (PDE). Although a significant breakthrough has been achieved with the recent introduction of a new device structure capable of combining a good timing resolution with a remarkable PDE in the near infrared region, nevertheless there is still room for further improvements. In this paper we will discuss further modifications to the device structure enabling the fabrication of arrays with red enhanced photon detection efficiency.

Recent demonstrations of GaN APDs with spatially uniform gain regions free of microplasmas reported multiplication gain (M) values of 10-25 (McIntosh et al, 1999; Carrano et al., 2000). We report here on photon counting, or Geiger-mode, measurements of GaN APDs which entail much greater avalanche gain (10/sup 4/<M<10/sup 8/). The photon detection efficiency (PDE) at 325 nm and dark count rate were measured as a function of the applied voltage bias. Measurements have been made using both passive-quench and gated-quench modes of operation. A PDE of 13% is found at a dark count rate of 400 kHz. The best devices exhibit leakage current less than 20 nA at 90% of breakdown voltage.

Single-photon avalanche diodes (SPADs) are high-performance light-sensitive sensors operating in low-light condition. Si-SPADs manufactured through standard CMOS fabrication process have advantages in terms of manufacturing cost, low power consumption, device shrinkage, and process stability compared to SPADs on custom fabrication. A deeper multiplication using deep n-well (DNW) improves key performances of Si-SPAD such as dark count rate (DCR) and photon detection efficiency (PDE). Here, the guard ring (GR) must be included for deep junction SPAD because light detection efficiency is lowered due to premature edge breakdown (PEB) generated by strong electric field at the edge. PEB affects not only the characteristics but also the manufacturing uniformity. Therefore, the DNW should be carefully designed to show better performance and stability for Si-SPADs. In this paper, the effects of electrical characteristics such as current-voltage (I-V) curve, DCR, off leakage, and breakdown voltage, and process stability on DNW implanted SPAD with GR variation are analyzed using actual fabricated SPAD measurement data and the calibrated technology computer-aided design (TCAD) simulated results. When the deep multiplication junction is formed using the higher ion implantation energy, the penetration effect and the process instability can be generated and it can also weaken the GR effect, which prevents PEB caused by having a stronger electric field than the multiplication zone. In addition, it is verified to prevent the risk of designing a Si-SPAD and die-to-die variation due to DNW implantation. Based on the results, deep junction design scheme for high resolution and mass production can be suggested.

A state of the art Back Illuminated (BI) Single Photon Avalanche Diode (SPAD) array sensor realized via a 90nm CMOS compatible process on a 300 mm silicon platform is reported in the following. The array consists of 10 μm pixels, each using a 7μm thick silicon active layer, which allows to extend the device's optical sensitivity up to the Near-Infrared (NIR) spectrum. Furthermore, buried metal Full Trench Isolation (FTI) was employed to suppress crosstalk (X-talk), a critical feature in a device sensitive enough to be triggered by a single electro-luminescence photon emitted by a neighboring pixel. Finally, in order to maximize the Fill Factor (F.F) and allow a BI structure, a Cu-Cu bonding process was carried out. Through process and device design optimization, not only a Photon Detection Efficiency (PDE) greater than 14% at λ= 940nm and low timing jitter were achieved, but also the best in class Dark Count Rate (DCR) as compared to previously reported SPAD sensors. These combined features pave the way towards efficient, eye-safe and cost-effective time of flight applications.

To increase contrast in positron emission tomography (PET) images, researchers are investigating detectors that reach below the nanosecond timing resolution. This allows a tight coincidence window which reduces random coincidence counts in the acquired data, as well as to include time-of-flight information into the reconstruction algorithms. With this goal in mind, single photon avalanche diode (SPAD) arrays have been under study for their excellent timing performances. However, their spurious dark counts can blur the start of PET signals where timing information is the most precise and create false starts in the acquisition system, introducing dead time. To minimize these problems in digital SPAD systems using a single time to digital converter (TDC) per PET channel, dark count discriminator circuits are required to reduce timing errors and increase the triggering efficiency in presence of dark counts. This paper compares the performance of a probabilistic and a novel delay line based dark count discriminator. Simulations of a SPAD array investigate the impact of dark counts on triggering efficiency and coincidence timing. Results show that the probabilistic discriminator provides excellent event recovery with regard to dark counts at the cost of some coincidence timing resolution. On the other hand, the delay line discriminator maintains the peak coincidence timing resolution but does not provide as much efficiency at high dark count rate levels.

Superconducting nanowire single-photon detectors are an ideal match for integrated quantum photonic circuits due to their high detection efficiency for telecom wavelength photons. Quantum optical technology also requires single-photon detection with low dark count rate and high timing accuracy. Here we present very low noise superconducting nanowire single-photon detectors based on NbTiN thin films patterned directly on top of Si3N4 waveguides. We systematically investigate a large variety of detector designs and characterize their detection noise performance. Milli-Hz dark count rates are demonstrated over the entire operating range of the nanowire detectors which also feature low timing jitter. The ultra-low dark count rate, in combination with the high detection efficiency inherent to our travelling wave detector geometry, gives rise to a measured noise equivalent power at the 10−20 W/Hz1/2 level.

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.

A sensor is fabricated by a two poly-four metal 0.35 μm CMOS process in order to operate in the Geiger mode. The chip consists of an 8 × 8 array of 67 × 67 μm2 pixels that can be readout in either a summing mode or sequential mode. The features of the CMOS single photon avalanche photodiode (CMOS SPAD) were analyzed. The pixels were then arranged in a 8 × 8 array and the possibility of the summing mode and the sequential mode was verified. The CMOS SPAD pixel has a fill factor of 17.4%. The breakdown voltage of the pixel was at 18.9 V, and the photon detection efficiency was 20% at the 550 nm wavelength. The dead time was 20 nsec, and the dark count rate was 10 kHz at and below the single photon level. The operation of both summing mode and sequential mode function was sucessful in the 8 × 8 array sensor.