Abstract-The DEPFET collaboration develops highly granular, ultra-transparent active pixel detectors for high-performance vertex reconstruction at future collider experiments. The characterization of detector prototypes has proven that the key principle, the integration of a first amplification stage in a detector-grade sensor material, can provide a comfortable signal to noise ratio of over 40 for a sensor thickness of 50-75 µm. ASICs have been designed and produced to operate a DEPFET pixel detector with the required read-out speed. A complete detector concept is being developed, including solutions for mechanical support, cooling and services. In this paper the status of DEPFET R & D project is reviewed in the light of the requirements of the vertex detector at a future linear e + e − collider.
a b s t r a c tThis paper presents an analysis of the maximum achievable fill-factor by a pixel detector of Geiger-mode avalanche photodiodes with the Chartered 130 nm/Tezzaron 3D process. The analysis shows that fillfactors between 66% and 96% can be obtained with different array architectures and a time-gated readout circuit of minimum area. The maximum fill-factor is achieved when the two-layer vertical stack is used to overlap the non-sensitive areas of one layer with the sensitive areas of the other one. Moreover, different sensor areas are used to further increase the fill-factor. A chip containing a pixel detector of the Geigermode avalanche photodiodes and aimed to future linear colliders has been designed with the Chartered 130 nm/Tezzaron 3D process to increase the fill-factor.
We describe the integration of techniques and technologies to develop a Point-of-Care for molecular diagnosis PoC-MD, based on a fluorescence lifetime measurement. Our PoC-MD is a low-cost, simple, fast, and easy-to-use general-purpose platform, aimed at carrying out fast diagnostics test through label detection of a variety of biomarkers. It is based on a 1-D array of 10 ultra-sensitive Single-Photon Avalanche Diode (SPAD) detectors made in a 0.18 μm High-Voltage Complementary Metal Oxide Semiconductor (HV-CMOS) technology. A custom microfluidic polydimethylsiloxane cartridge to insert the sample is straightforwardly positioned on top of the SPAD array without any alignment procedure with the SPAD array. Moreover, the proximity between the sample and the gate-operated SPAD sensor makes unnecessary any lens or optical filters to detect the fluorescence for long lifetime fluorescent dyes, such as quantum dots. Additionally, the use of a low-cost laser diode as pulsed excitation source and a Field-Programmable Gate Array (FPGA) to implement the control and processing electronics, makes the device flexible and easy to adapt to the target label molecule by only changing the laser diode. Using this device, reliable and sensitive real-time proof-of-concept fluorescence lifetime measurement of quantum dot QdotTM 605 streptavidin conjugate is demonstrated.
The gated operation is proposed as an effective method to reduce the noise in pixel detectors based on Geiger mode avalanche photodiodes. A prototype with the sensor and the front-end electronics monolithically integrated has been fabricated with a conventional HV-CMOS process. Experimental results demonstrate the increase of the dynamic range of the sensor by applying this technique.Introduction: Avalanche photodiodes reverse biased above the breakdown voltage (V BD ) in the so-called Geiger mode (GAPDs) can be used to detect single charge carriers thanks to the self-sustaining avalanche multiplication process, provided that proper quenching and readout electronics are employed [1]. In particular, the high intrinsic sensitivity of GAPDs together with the feasibility of on-chip integration of the sensor and the front-end electronics enabled by CMOS technologies [2] can be of benefit in various fields, such as 3D imaging for bio-applications, time-of-flight (TOF) ranging, astronomical observations and high energy physics (HEP) experiments [3]. However, the high intrinsic gain also generates false avalanches that cannot be distinguished from real events and increases the intrinsic sensor noise. Spurious avalanches caused by thermal or tunnel carriers are called dark counts. The dark count rate (DCR) depends on the technology, the sensitive area, the reverse bias overvoltage (V OV ) and the temperature. Moreover, correlated pulses due to the random release of carriers that were trapped during a previous avalanche are known as afterpulses. The afterpulsing probability is a function of the trap density, the number of carriers involved in an avalanche and the lifetime of these carriers.The efforts reported in the literature related to the reduction of the noise in GAPD detectors consider dedicated technologies [4] and quenching circuits that delay the recharge of the device [5] or minimise either the charge flow [6] or the duration of the avalanche process [7]. Whereas the former requires high-cost technologies, the last three consider only the reduction of afterpulses. Apart from that, in those applications in which the arrival time of charge carriers is known it is also possible to use the gated mode operation to improve the performance of the detector. Although this technique has already been used to reduce dark counts and afterpulses in InGaAs/InP detectors [8], to the best of our knowledge it is the first time that the gated acquisition for decreasing the noise in a GAPD pixel detector monolithically integrated is reported.
Miniaturization of sensors and actuators up to the point of active features in endoscopic capsules, such as locomotion or surgery, is a challenge. VECTOR endoscopic capsule has been designed to be the first endoscopic capsule with active locomotion. It is equipped with mini-legs driven by Brushless DC (BLDC) micro motors. In addition it can be also equipped with some other sensors and actuators, like a liquid lens, that permits to enable advanced functions. Those modules are managed by an Application Specific Integrated Circuit (ASIC) specifically designed for the VECTOR capsule. The ASIC is a complete System-On-Chip (SoC) and integrates all the electronics needed to enable the legged locomotion and the sensing and actuating functions of the capsule in an unique chip. The SoC also permits other functions for endoscopic capsules such as drug delivery and biopsy. The size of the SoC is 5.1 mm x 5.2 mm in a 0.35 µm high voltage CMOS technology.
Microrobots were proposed more than 20 years ago but it has proven challenging to integrate a power system and actuators into some few mm 3 . There have been some attempts to create an autonomous mobile microrobot but any has been successful. Moreover, the proposed microrobots were simply mobile platforms incapable of sensing its environment and taking decisions. I-SWARM has been designed to be a real autonomous microrobot. It is powered by solar cells and provided with a locomotion unit for moving, an IR module for communicating and a contact tip for detecting near objects. Those modules are managed by an ASIC designed specifically for I-SWARM. All the electronics (power electronics, buffers, ADCs, DACs, control unit, analog transducers and an oscillator) have been embedded in the ASIC due to the limited area, 3 x 3 mm 2 . The ASIC is a complete System On Chip (SoC) that has several features not reported before in any circuit for microrobots: communicate and act cooperatively with other I-SWARM microrobots, detect near objects, measure distance to an object, light trailing and reprogramability. This paper gives some guidelines to design integrated circuits for microrobots. A Fig. 1. Block diagram of the major electronics circuits for a microrobot.
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