Standard Silicon Detectors Research Articles

TCAD simulations of non-irradiated and irradiated low-gain avalanche diodes and comparison with measurements

In this work, the results of Technology-CAD (TCAD) device-level simulations of non-irradiated and irradiated Low-Gain Avalanche Diode (LGAD) detectors and their validation against experimental data will be presented. Thanks to the intrinsic multiplication of the charge within these silicon sensors, it is possible to improve the signal to noise ratio thus limiting its drastic reduction with fluence, as it happens instead for standard silicon detectors. Therefore, special attention has been devoted to the choice of the avalanche model, which allows the simulation findings to better fit with experimental data. Moreover, a radiation damage model (called “New University of Perugia TCAD model”) has been fully implemented within the simulation environment, to have a predictive insight into the electrical behavior and the charge collection properties of the LGAD detectors, up to the highest particle fluences expected in the future High Energy Physics (HEP) experiments. This numerical model allows to consider the comprehensive bulk and surface damage effects induced by radiation on silicon sensors. By coupling the “New University of Perugia TCAD model” with an analytical model that describes the mechanism of acceptor removal in the multiplication layer, it has been possible to reproduce experimental data with high accuracy, demonstrating the reliability of the simulation framework.

Detector-electrode for alpha spectrometry in water sample, numerical and early feasibility investigation toward thermocompression bonding assembly process

This study focuses on the feasibility of a detector-electrode for direct alpha measurement in aqueous samples. Such a device could be made by adding a boron doped diamond electrode on top of a standard silicon detector, with bonding and insulating layers. The impact of these different layers has been investigated by Monte-Carlo simulation (MCNP6), to find a compromise between alpha detection of the silicon, electrode and shielding properties of the diamond. The assembly process involving thermocompression between both substrates was successfully achieved under a clean room conditions.

Testing of a Prototype Detector of Heavy Charged Particles Based on Diamond Epitaxial Films Obtained by Gas-Phase Deposition

The results of testing a prototype of a surface-barrier detector of charged particles based on single-crystal epitaxial layers of diamond are presented. Diamond films with p-type conduction with a boron concentration of (4–8) × 1014 cm–3 65 μm thick were grown using gas-phase deposition on heavily doped diamond substrates grown at high pressure and high temperature. A 17 mm2 Schottky barrier was formed by sputtering Pt with a thickness of 30 nm. When irradiated from the 238Pu α-source (the 5.499 keV line) a detector with an external bias of 90 V demonstrated a charge collection efficiency close to 100% and a FWHM high energy resolution of 0.56%. The obtained energy resolution is at the level of standard silicon detectors.

Upconversion detection of long-wave infrared radiation from a quantum cascade laser

Broadly tunable upconversion is demonstrated for long-wave infrared (LWIR) detection. The upconversion system is evaluated by the detection of 50 ns pulses from a narrow linewidth tunable quantum cascade laser (QCL) in the 9.4 to 12 µm range. The LWIR signal is mixed with a 1064 nm laser beam in a silver gallium sulfide (AgGaS2) crystal, resulting in an upconverted signal in the 956 to 977 nm range, using angle tuning for optimal phase-matching. This allows for efficient, high speed detection using a standard silicon detector. A theoretical model including absorption and diffraction shows qualitative agreement with experimental data.

Development of Ultra-Fast Silicon Detectors for 4D tracking

In this contribution we review the progress towards the development of a novel type of silicon detectors suited for tracking with a picosecond timing resolution, the so called Ultra-Fast Silicon Detectors. The goal is to create a new family of particle detectors merging excellent position and timing resolution with GHz counting capabilities, very low material budget, radiation resistance, fine granularity, low power, insensitivity to magnetic field, and affordability. We aim to achieve concurrent precisions of ∼ 10 ps and ∼ 10 μm with a 50 μm thick sensor. Ultra-Fast Silicon Detectors are based on the concept of Low-Gain Avalanche Detectors, which are silicon detectors with an internal multiplication mechanism so that they generate a signal which is factor ∼10 larger than standard silicon detectors. The basic design of UFSD consists of a thin silicon sensor with moderate internal gain and pixelated electrodes coupled to full custom VLSI chip. An overview of test beam data on time resolution and the impact on this measurement of radiation doses at the level of those expected at HL-LHC is presented. First I-V and C-V measurements on a new FBK sensor production of UFSD, 50 μm thick, with B and Ga, activated at two diffusion temperatures, with and without C co-implantation (in Low and High concentrations), and with different effective doping concentrations in the Gain layer, are shown. Perspectives on current use of UFSD in HEP experiments (UFSD detectors have been installed in the CMS-TOTEM Precision Protons Spectrometer for the forward physics tracking, and are currently taking data) and proposed applications for a MIP timing layer in the HL-LHC upgrade are briefly discussed.

Dependence of charge multiplication on different design parameters of LGAD devices

The Low Gain Avalanche Detectors (LGADs) have the unique characteristic to provide amplification to the particle signal by using a controlled local avalanche mechanism. These devices are being explored by the HEP community because, while it is known that in standard silicon detectors the signal-to-noise ratio falls drastically with fluence, in LGAD devices this can be made sufficiently high to potentially overcome this problem. However, the existing irradiation studies show that at high fluences, the LGAD internal gain disappears and is no more significant. In this work, we have studied the effect of various design parameters of the LGAD device on its gain characteristic, at different irradiation levels. With the acquired understanding, we have also tried to tune the LGAD gain so to be suited for operation in a high radiation environment.

Ultra-Fast Silicon Detectors for 4D tracking

We review the progress toward the development of a novel type of silicon detectors suited for tracking with a picosecond timing resolution, the so called Ultra-Fast Silicon Detectors. The goal is to create a new family of particle detectors merging excellent position and timing resolution with GHz counting capabilities, very low material budget, radiation resistance, fine granularity, low power, insensitivity to magnetic field, and affordability. We aim to achieve concurrent precisions of ∼ 10 ps and ∼ 10 μm with a 50 μm thick sensor. Ultra-Fast Silicon Detectors are based on the concept of Low-Gain Avalanche Detectors, which are silicon detectors with an internal multiplication mechanism so that they generate a signal which is factor ∼ 10 larger than standard silicon detectors.

Parametric generation and characterization of femtosecond mid-infrared pulses in ZnGeP2.

Ultrafast mid-infrared (IR) coherent radiation plays an important role in strong-field physics, wherein the use of longer wavelengths has reduced the optical intensities needed to drive light-matter interactions by orders of magnitude in comparison to near-IR radiation. Optimizing parametric interactions for generation and characterization of mid-IR pulses is an enabling step for those applications. We report on the production of >50 µJ femtosecond pulses centered at 5 µm in a two-stage optical parametric amplifier (OPA) based on ZnGeP2, a high-performance optical material in this spectral region. The OPA is pumped by an ultrafast 2-µm source. Amplified pulses have been characterized by parametric upconversion, enabling the use of standard silicon detectors. A numerical model of the system has been developed and tested to control dispersion, group-velocity mismatch, and off-axis parametric fluorescence. The source architecture is suitable for production of mJ-level mid-IR ultrafast pulses without the use of chirped-pulse amplification, where convenient pumping could be realized directly by mid-IR laser sources based on materials such as Cr:ZnSe or Cr:ZnS.

Improvements in data analysis obtained by large-area silicon ΔE - E detector telescopes

The paper describes a few practical methods for the analysis of data obtained by standard thin-thick silicon detector telescopes used in nuclear reaction measurements. The addressed issues are: 1) improvement in double-sided silicon strip detector (DSSSD) calibration based on the fact that each event is registered twice, both in horizontal and vertical strips, 2) improvements in particle identification and 3) simplified mapping of the non-uniformity of the thin detector, without a dedicated measurement of the thickness. The proposed procedures are applied on experimental data obtained for 30MeV 7Li beam induced reactions on LiF and C targets, studied with a detection setup consisting of four telescopes placed at different angles and distances. The proposed methods aim at quicker and more reliable calibration and particle identification.

Two-proton radioactivity: 10 years of experimental progresses

The two-proton radioactivity has been observed experimentally in 2002, at projectile fragmentation facilities, more than 40 years after the first theoretical prediction of this process. First observations were indirect measurements, using standard silicon detector devices. Since then, a new generation of experiments allowed for a direct observation, and opened the field of more detailed studies, using tracking devices for the detection of the emitted protons.

The VERDI fission fragment spectrometer

The VERDI time-of-flight spectrometer is dedicated to measurements of fission product yields and of prompt neutron emission data. Pre-neutron fission-fragment masses will be determined by the double time-of-flight (TOF) technique. For this purpose an excellent time resolution is required. The time of flight of the fragments will be measured by electrostatic mirrors located near the target and the time signal coming from silicon detectors located at 50 cm on both sides of the target. This configuration, where the stop detector will provide us simultaneously with the kinetic energy of the fragment and timing information, significantly limits energy straggling in comparison to legacy experimental setup where a thin foil was usually used as a stop detector. In order to improve timing resolution, neutron transmutation doped silicon will be used. The high resistivity homogeneity of this material should significantly improve resolution in comparison to standard silicon detectors. Post-neutron fission fragment masses are obtained form the time-of-flight and the energy signal in the silicon detector. As an intermediary step a diamond detector will also be used as start detector located very close to the target. Previous tests have shown that poly-crystalline chemical vapour deposition (pCVD) diamonds provides a coincidence time resolution of 150 ps not allowing complete separation between very low-energy fission fragments, alpha particles and noise. New results from using artificial single-crystal diamonds (sCVD) show similar time resolution as from pCVD diamonds but also sufficiently good energy resolution.

Test Beam Characterization of 3-D Silicon Pixel Detectors

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Three-dimensional (3-D) silicon detectors are characterized by cylindrical electrodes perpendicular to the surface and penetrate into the bulk material in contrast to standard Si detectors with planar electrodes on the top and bottom. This geometry renders them particularly interesting to be used in environments where standard silicon detectors have limitations, such as, for example, the radiation environment expected in an upgrade to the Large Hadron Collider at CERN. For the first time, several 3-D sensors were assembled as hybrid pixel detectors using the ATLAS-pixel front-end chip and readout electronics. Devices with different electrode configurations have been characterized in a 100 GeV pion beam at the CERN SPS. Here, we report results on unirradiated devices with three 3–D electrodes per 50<formula formulatype="inline"> <tex Notation="TeX">$\,\times \,$</tex></formula>400 <formula formulatype="inline"> <tex Notation="TeX">$\mu {\rm m}^{2}$</tex></formula> pixel area. Full charge collection is obtained already with comparatively low bias voltages around 10 V. Spatial resolution with binary readout is obtained as expected from the cell dimensions. Efficiencies of 95.9%<formula formulatype="inline"><tex Notation="TeX">$ \pm$</tex></formula>0.1% for tracks incident parallel to the electrodes and of 99.9%<formula formulatype="inline"><tex Notation="TeX">$ \pm$</tex></formula>0.1% for tracks incident at 15<formula formulatype="inline"> <tex Notation="TeX">$^{\circ}$</tex></formula> are measured. The homogeneity and charge sharing of the efficiency over the pixel area are measured. </para>

Avalanche breakdown in silicon devices for contactless logic testing and optical interconnect

A silicon p---n junction that is biased in avalanche breakdown mode emits visible light. Although the efficiency of such silicon emitters is poor, their ability to modulate at GHz frequencies make them a good choice for many applications including optical interconnect and optical contactless logic testing. Results demonstrate the feasibility of an all silicon optical interconnect system and an all silicon contactless testing methodology using the silicon light emitter and standard silicon detectors. The development of truly efficient silicon light emitting would enable many new applications.

Development of radiation tolerant semiconductor detectors for the Super-LHC

The envisaged upgrade of the Large Hadron Collider (LHC) at CERN towards the Super-LHC (SLHC) with a 10 times increased luminosity of 10 35 cm −2 s −1 will present severe challenges for the tracking detectors of the SLHC experiments. Unprecedented high radiation levels and track densities and a reduced bunch crossing time in the order of 10 ns as well as the need for cost effective detectors have called for an intensive R&D program. The CERN RD50 collaboration “Development of Radiation Hard Semiconductor Devices for Very High Luminosity Colliders” is working on the development of semiconductor sensors matching the requirements of the SLHC. Sensors based on defect engineered silicon like Czochralski, epitaxial and oxygen enriched silicon have been developed. With 3D, Semi-3D and thin detectors new detector concepts have been evaluated and a study on the use of standard and oxygen enriched p-type silicon detectors revealed a promising approach for radiation tolerant cost effective devices. These and other most recent advancements of the RD50 collaboration are presented.

Time dependent 14MeV neutrons measurement using a polycrystalline chemical vapor deposited diamond detector at the JET tokamak

A polycrystalline chemical vapor deposited (CVD) diamond detector was installed on a JET tokamak in order to monitor the time dependent 14MeV neutron emission produced by D–T plasma pulses during the Trace Tritium Experiment (TTE) performed in October 2003. This was the first tentative ever attempted to use a CVD diamond detector as neutron monitor in a tokamak environment. Despite its small active volume, the detector was able to detect the 14MeV neutron emission (&amp;gt;1.0×1015n∕shot) with good reliability and stability during the experimental campaign that lasted five weeks. The comparison with standard silicon detectors presently used at JET as 14MeV neutron monitors is reported, showing excellent correlation between the measurements. The results prove that CVD diamond detectors can be reliably used in a tokamak environment and therefore confirm the potential of this technology for next step machines like ITER.

Bulk damage effects in standard and oxygen-enriched silicon detectors induced by 60Co-gamma radiation

The influence of oxygen in silicon on bulk damage effects induced by 60Co-gamma irradiation has been studied in a dose range between 0.2 and 900Mrad. The detector processing and oxygen enrichment were carried out in a common project by the Institute of Micro-sensors CiS using n-type high-resistivity FZ silicon (3–6kΩcm) with 〈111〉 and 〈100〉 orientation. Different oxygen concentrations were achieved by diffusion at 1150°C for 24, 48 and 72h. This report on bulk damage effects is focussed on the observed changes in the reverse current, the effective space charge density Neff extracted from C/V measurements and investigations using the transient current technique. A substantial improvement of radiation hardness concerning the development of the macroscopic properties was found for detectors manufactured on oxygenated material compared to standard material. It will be demonstrated that the change of the effective space charge density as well as the increase of the reverse current can be attributed to the creation of two deep acceptor levels and a shallow donor level.

Deep defect levels in standard and oxygen enriched silicon detectors before and after 60Co-γ-irradiation

Capacitance Deep Level Transient Spectroscopy (C-DLTS) measurements have been performed on standard and oxygen-doped silicon detectors manufactured from high-resistivity n-type float zone material with 〈1 1 1〉 and 〈1 0 0〉 orientation. Three different oxygen concentrations were achieved by the so-called diffusion oxygenated float zone (DOFZ) process initiated by the CERN-RD48 (ROSE) collaboration. Before the irradiation a material characterization has been performed. In contrast to radiation damage by neutrons or high-energy charged hadrons, were the bulk damage is dominated by a mixture of clusters and point defects, the bulk damage caused by 60Co-γ-radiation is only due to the introduction of point defects. The dominant electrically active defects which have been detected after 60Co-γ-irradiation by C-DLTS are the electron traps VO i, C iC s, V 2(=/−), V 2(−/0) and the hole trap C iO i. The main difference between standard and oxygenated silicon at low dose values can be seen in the introduction rate of C iC s compared to C iO i. For highly oxygenated silicon the introduction of C iC s is fully suppressed, while the sum of the introduction rates g(C iC s)+ g(C iO i) is independent on the oxygen concentration.

Improved radiation hardness to low-energy protons for oxygenated Si detectors with thermal donors

Silicon detectors have been made on oxygenated silicon with the incorporation of thermal donors during the oxidation process based on BNL's high-temperature long-time (thermal donor) (HTLT(TD)) technology. The initial doping concentration in HTLT(TD) silicon detectors is twice more than that of standard silicon detectors (same starting material, but no HTLT process), with TD being the dominant donor. Standard and HTLT(TD) silicon detectors have been irradiated by 10 MeV protons up to 2.5×10 14 p/ cm 2 . It has been found that the increase rate ( β) of the space charge concentration ( N eff) after space charge sign inversion (SCSI) in HTLT(TD) silicon detectors is about half of that in standard silicon detectors. Further improvement in proton radiation hardness has been observed in terms of the SCSI fluence. The SCSI fluence for HTLT(TD) silicon detectors is more than four times higher than that of standard detectors, although the corresponding ratio of initial space charge concentrations between the two groups of detectors is about two. This result implies that the SCSI is greatly delayed in HTLT(TD) silicon detector compared with silicon detectors with similar initial space charge (all phosphorus) concentration (lower resistivity standard silicon detectors).

Results of irradiation tests on standard planar silicon detectors with 7– [formula omitted] protons

Standard planar silicon detectors of 2 kΩ cm resistivity were irradiated with 7– 10 MeV protons up to fluences of 7×10 13 p/ cm 2 . The effects of proton irradiation on the effective doping concentration ( N eff) and leakage current ( I vol) as a function of fluence were investigated. The evolution of N eff and I vol as a function of time after irradiation was obtained by heating the detectors to accelerate their ageing. Comparison is done with detectors of the same type irradiated with 24 GeV/ c protons. The hardness factors for 7– 10 MeV protons are extracted.

Review on the development of cryogenic silicon detectors

In this paper, we report on the performance of heavily irradiated silicon detectors operated at cryogenic temperatures. The results discussed here show that cryogenic operation indeed represents a reliable method to increase the radiation tolerance of standard silicon detectors by more than one order of magnitude. In particular, a 400 μm thick “double-p” silicon detector irradiated up to 1×10 15 n/cm 2 delivers a mip signal of about 27 000 electrons when operated at 130 K and 500 V bias. The position resolution of an irradiated microstrip detector, and “in situ” irradiation of a pad detector during operation in the cold are also discussed.