This paper introduces a new concept of silicon radiation detector with intrinsic multiplication of the charge, called Low Gain Avalanche Detector (LGAD). These new devices are based on the standard ...Avalanche Photo Diodes (APD) normally used for optical and X-ray detection applications. The main differences to standard APD detectors are the low gain requested to detect high energy charged particles, and the possibility to have fine segmentation pitches: this allows fabrication of microstrip or pixel devices which do not suffer from the limitations normally found 1 in avalanche detectors. In addition, a moderate multiplication value will allow the fabrication of thinner devices with the same output signal of standard thick substrates.
The investigation of these detectors provides important indications on the ability of such modified electrode geometry to control and optimize the charge multiplication effect, in order to fully recover the collection efficiency of heavily irradiated silicon detectors, at reasonable bias voltage, compatible with the voltage feed limitation of the CERN High Luminosity Large Hadron Collider (HL-LHC) experiments 2. For instance, the inner most pixel detector layers of the ATLAS tracker will be exposed to fluences up to 2×10161MeVneq/cm2, while for the inner strip detector region fluences of 1×1015neq/cm2 are expected.
The gain implemented in the non-irradiated devices must retain some effect also after irradiation, with a higher multiplication factor with respect to standard structures, in order to be used in harsh environments such those expected at collider experiments.
Timing performance of small cell 3D silicon detectors Kramberger, G.; Cindro, V.; Flores, D. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2019, Letnik:
934
Journal Article
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A silicon 3D detector with a single cell of 50 × 50 μm2 was produced and evaluated for timing applications. The measurements of time resolution were performed for 90Sr electrons with dedicated ...electronics used also for determining time resolution of Low Gain Avalanche Detectors (LGADs). The measurements were compared to those with LGADs and also simulations. The studies showed that the dominant contribution to the timing resolution comes from the time walk originating from different induced current shapes for hits over the cell area. This contribution decreases with higher bias voltages, lower temperatures and smaller cell sizes. It is around 30 ps for a 3D detector of 50 × 50 μm2 cell at 150 V and −20 °C, which is comparable to the time walk due to Landau fluctuations in LGADs. It even improves for inclined tracks and larger pads composed of multiple cells. A good agreement between measurements and simulations was obtained, thus validating the simulation results.
A Transient Current Technique (TCT) utilizing an IR laser with 100 ps pulse width and beam diameter of FWHM = 8 μm was used to evaluate non-irradiated and irradiated p-type silicon micro-strip ...detectors. The beam was parallel with the surface and perpendicular to the strips (Edge-TCT) so that the electron hole pairs were created at known depth in the detector. Induced current pulses were measured in one of the strips. The pulse shapes were analyzed in a new way, which does not require the knowledge of effective trapping times, to determine drift velocity, charge collection and electric field profiles in heavily irradiated silicon detectors. The profiles were studied at different laser beam positions (depth of carrier generation), voltages and fluences up to 5·10 15 neutrons cm -2 . A strong evidence for charge multiplication at high voltages was found with the detector irradiated to the highest fluence.
This paper presents the results of edge-Transient Current Technique (e-TCT) measurements of a test structure of a High Voltage CMOS (HV-CMOS) pixel demonstrator, the H35DEMO. Several high resistivity ...(1000 Ω⋅cm) samples of the device were thinned to 100μm, processed for backside biasing, and irradiated with neutrons to fluences up to 2⋅1016neq⋅cm−2. The evolution of effective doping concentration with respect to fluence is studied. Samples irradiated to a fluence of 5⋅1014neq⋅cm−2 are fully depleted beyond −50V substrate bias voltage while samples irradiated to the highest fluence reach 30 μm depletion at −200V.
Fluence profiling at JSI TRIGA reactor irradiation facility Sola, V.; Mandić, I.; Ambrožič, K. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
June 2024, 2024-06-00, Letnik:
1063
Journal Article
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We present an analysis of the fluence profile at the JSI TRIGA neutron reactor facility in Ljubljana. For the study, multi-pad Low-Gain Avalanche Diodes (LGADs) are used. The deactivation of acceptor ...doping in the gain layer implant due to the irradiation, typical of LGAD devices, is exploited to map the fluence profile inside the irradiation channels. The amount of active doping of the LGAD gain layer is extracted via capacitance–voltage measurements for each pad before and after irradiation to a fluence of 1.5 × 1015neq/cm2, where neq stands for 1 MeV equivalent neutron count, providing a precise and prompt measurement of the fluence distribution over the LGAD sensor. Experimental results are compared to neutron fluence expectations calculated with Monte Carlo techniques.
Carotenoids are versatile isoprenoids that are important in food quality and health promotion. There is a need to establish recommended dietary intakes nutritional reference values for carotenoids. ...Research on carotenoids in agro-food and health is being propelled by the two multidisciplinary international networks, the Ibero-American Network for the Study of Carotenoids as Functional Foods Ingredients (IBERCAROT;
http: www.cyted.org
) and the European Network to Advance Carotenoid Research and Applications in Agro-Food and Health (EUROCAROTEN;
http: www.eurocaroten.eu
). In this review, considerations for their safe and sustainable use in products mostly intended for health promotion are provided. Specifically, information about sources, intakes, and factors affecting bioavailability is summarized. Furthermore, their health-promoting actions and importance in public health in relation to the contribution of reducing the risk of diverse ailments are synthesized. Definitions and regulatory and safety information for carotenoid-containing products are provided. Lastly, recent trends in research in the context of sustainable healthy diets are summarized.
Gain dependence on free carrier concentration in LGADs Kramberger, G.; Hiti, B.; Cindro, V. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
01/2023, Letnik:
1046
Journal Article
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Low gain avalanche detectors (LGADs) were investigated with transient current technique utilizing 1064 nm light to determine the effect of ionization density on the measured gain. The ionization ...density was varied with laser intensity and width of the beam spot. A model was derived explaining the decrease of gain due to the polarization of the gain layer, which reduces the electric field. The model was also tested at different ionization densities for LGADs of different gain layer design.
The edge transient-current technique (Edge-TCT) and charge-collection measurements with passive test structures made with the LFoundry 150-nm CMOS process on a p-type substrate with an initial ...resistivity of over 3 kΩcm are presented. The measurements were made before and after irradiation with reactor neutrons up to 2⋅1015 neq/cm2. Two sets of devices were investigated: unthinned (700 μm) with the substrate biased through the implant on top and thinned (200 μm) with a processed and metallised backplane.
The depletion depth was estimated with the Edge-TCT and the collected charge was measured with a 90Sr source using an external amplifier having a 25-ns shaping time. The depletion depth for a given bias voltage decreased with the increasing neutron fluence, but it was still larger than 70 μm at 250 V after the highest fluence. After irradiation a much higher collected charge was measured for the thinned detectors with a processed backplane compared to the unthinned devices, although the same or an even larger depletion depth was measured in the unthinned devices. The most probable value of the collected charge of over 5000 electrons was measured with a thinned device also after irradiation to 2⋅1015 neq/cm2. This is sufficient to ensure the successful operation of these detectors at the outer layer of the pixel detector in the ATLAS experiment at the upgraded HL-LHC.
Experimental Study of Acceptor Removal in UFSD Jin, Y.; Ren, H.; Christie, S. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2020, Letnik:
983, Številka:
C
Journal Article
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The performance of the Ultra-Fast Silicon Detectors (UFSD) after irradiation with neutrons and protons is compromised by the removal of acceptors in the thin layer below the junction responsible for ...the gain. This effect is tested both with capacitance–voltage, C–V, measurements of the doping concentration and with measurements of charge collection, CC, using charged particles. We find a perfect linear correlation between the bias voltage to deplete the gain layer determined with C–V and the bias voltage to collect a defined charge, measured with charge collection. An example for the usefulness of this correlation is presented.
Studies of annealing at temperatures up to 450 °C with Low Gain Avalanche Detectors (LGAD) irradiated with neutrons are described. It was found that the performance of LGADs irradiated with 1.5e15 ...n/cm2 was already improved at 5 min of annealing at 250 °C. Isochronal annealing for 30 min in 50 °C steps between 300 °C and 450 °C showed that the largest beneficial effect of annealing is at around 350 °C. Another set of devices was annealed for 60 min at 350 °C and this annealing significantly increased depletion voltage of the gain layer (Vgl). The effect is equivalent to reducing the effective acceptor removal constant by a factor of ∼ 4. Increase of Vgl is the consequence of increased effective space charge in the gain layer caused by formation of electrically active defects or re-activation of interstitial boron atoms.
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