Polarization of silicon detectors by minimum ionizing particles Dezillie, B.; Eremin, V.; Li, Z. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2000, Letnik:
452, Številka:
3
Journal Article
Recenzirano
This work presents quantitative predictions of the properties of highly irradiated (e.g. by high-energy particles, up to an equivalent fluence of 1×10
14
n
cm
−2) silicon detectors operating at ...cryogenic temperature. It is shown that the exposure to the Minimum Ionising Particle (MIP) with counting rates of about 10
6
cm
−2
s
−1 can influence the electric field distribution in the detector's sensitive volume. This change in the electric field distribution and its effect on the charge collection efficiency are discussed in the frame of a model based on trapping of carriers generated by MIPs. The experiment was performed at 87
K with an infrared (1030
nm) laser to simulate MIPs.
Silicon detectors fabricated by BNLs high-temperature, long time (HTLT) oxidation technology have been characterized using various techniques for material/detector properties and radiation hardness ...with respect to gamma, proton and neutron irradiation. It has been found that a uniform oxygen distribution with a concentration of 4×10
17/cm
3 has been achieved in high-resistivity FZ silicon with our HTLT technology. With the standard HTLT technology, the original high resistivity of FZ silicon will be retained. However, the controlled introduction of thermal donors (TD) with a concentration higher than the original shallow doping impurity can be achieved with a process slightly altered from the standard HTLT technology (HTLT-TD). Detectors made by both technologies (HTLT and HTLT-TD) have been found to be advantageous in radiation hardness to gamma and proton irradiation, in terms of detector full depletion voltage degradation, as compared to the control samples. In fact, these detectors are insensitive to gamma irradiation up to 600
Mrad and more tolerant by at least a factor of two to proton irradiation and the following reverse annealing. However, there is little improvement in radiation hardness to neutron irradiation, which has been attributed to the nature of neutron-induced damage that is dominated by extended defects or defect clusters. Microscopic measurements (I-DLTS) have also been made on control and HTLT samples and will be compared and presented.
The radiation hardness for fast neutrons, high energy protons and /sup 60/Co gamma rays of planar detectors processed from highly oxygenated silicon detectors obtained by using high temperature ...(1200/spl deg/C), long time (> 200 hours) oxidation technology, are compared with standard silicon detectors. For fast neutron irradiation it is found that there is no advantage of using highly oxygenated silicon FZ detectors as compared to the standard ones in terms of full depletion voltage degradation as measured a few days after radiation. For a gamma ray dose of 250 Mrad, the standard detectors of all resistivities (1 k/spl Omega/cm to 5.6 k/spl Omega/cm) invert the space charge sign, while there is little change in space charge density for oxygenated ones. For proton irradiation, the rate in full depletion voltage increase (/spl beta/) is 2.3 times less than that fur neutron irradiation. The difference in radiation hardness is explained in terms of effect of radiation induced disorder regions (clusters of vacancies) on the introduction rates of divacancies in the oxygenated silicon.
The recovery of the charge collection efficiency (CCE) at low temperatures, the so-called ”Lazarus effect”, was studied in Si detectors irradiated by fast reactor neutrons, by protons of medium and ...high energy, by pions and by gamma-rays. The experimental results show that the Lazarus effect is observed: (a) after all types of irradiation; (b) before and after space charge sign inversion; (c) only in detectors that are biased at voltages resulting in partial depletion at room temperature. The experimental temperature dependence of the CCE for proton-irradiated detectors shows non-monotonic behaviour with a maximum at a temperature defined as the CCE recovery temperature. The model of the effect for proton-irradiated detectors agrees well with that developed earlier for detectors irradiated by neutrons. The same midgap acceptor-type and donor-type levels are responsible for the Lazarus effect in detectors irradiated by neutrons and by protons. A new, abnormal “zigzag”-shaped temperature dependence of the CCE was observed for detectors irradiated by all particles (neutrons, protons and pions) and by an ultra-high dose of γ-rays, when operating at low bias voltages. This effect is explained in the framework of the double-peak electric field distribution model for heavily irradiated detectors. The redistribution of the space charge region depth between the depleted regions adjacent to p+ and n+ contacts is responsible for the “zigzag”- shaped curves. It is shown that the CCE recovery temperature increases with reverse bias in all detectors, regardless of the type of radiation.
Detectors made on the silicon wafers with high concentration of thermal donors (TD), which were introduced during the high temperature long time (HTLT) oxygenation procedure, have been investigated ...in the study of radiation hardness with regard to neutron irradiation and donor removal problems in irradiated high resistivity Si detectors. Two facts have been established as the evidence of radiation hardness improvement of HTLT(TD) Si detectors irradiated below ∼10
14
n/cm
2 compared to detectors made on standard silicon wafers: the increase of space charge sign inversion fluence (of 1
MeV neutrons) due to lower initial Si resistivity dominated by TD, and the gain in the reverse annealing time constant
τ favourable for this material. Coupled with extremely high radiation tolerance to protons observed earlier (“beta zero” behaviour in a wide range of fluence), detectors from HTLT(TD) Si may be unique for application in the experiments with multiple radiations.
The changes in the effective space charge density (
N
eff) in as-irradiated detectors as a function of neutron fluence have been fitted using three different models. It has been shown that a new model with a universal donor removal rate for both materials, and considering the contribution of non-removable TD to the
N
eff provides good fit to the experimental data. A defect level related to TD has been observed in DLTS spectra of HTLT Si(TD) near
T∼75
K. The physics of donor removal in irradiated silicon detectors is discussed.
The charge collection efficiency (CCE) of heavily irradiated silicon diode detectors was investigated at temperatures between 77 and 200
K. The CCE was found to depend on the radiation dose, bias ...voltage value and history, temperature, and bias current generated by light. The detector irradiated to the highest fluence 2×10
15
n/cm
2 yields a MIP signal of at least 15000
e
− both at 250
V forward bias voltage, and at 250
V reverse bias voltage in the presence of a light-generated current. The “Lazarus effect” was thus shown to extend to fluences at least ten times higher than was previously studied.
A comparative study of the radiation hardness of single pad detectors, manufactured from standard float-zone (FZ) and epitaxial (Epi) n-type monocrystal silicon with comparable initial resistivity is ...presented. Detectors processed from FZ and Epi material with a low (400
Ω
cm and 500
Ω
cm) and a high (∼2
kΩ
cm) initial resistivity have been irradiated up to 4×10
14
n/cm
2 and measured under the same conditions in order to study the influence of the initial resistivity on the detector radiation hardness.
The RD48 (ROSE) collaboration has succeeded to develop radiation hard silicon detectors, capable to withstand the harsh hadron fluences in the tracking areas of LHC experiments. In order to reach ...this objective, a defect engineering technique was employed resulting in the development of Oxygen enriched FZ silicon (DOFZ), ensuring the necessary O-enrichment of about 2×10
17 O/cm
3 in the normal detector processing. Systematic investigations have been carried out on various standard and oxygenated silicon diodes with neutron, proton and pion irradiation up to a fluence of 5×10
14
cm
−2 (1
MeV neutron equivalent). Major focus is on the changes of the effective doping concentration (depletion voltage). Other aspects (reverse current, charge collection) are covered too and the appreciable benefits obtained with DOFZ silicon in radiation tolerance for charged hadrons are outlined. The results are reliably described by the “Hamburg model”: its application to LHC experimental conditions is shown, demonstrating the superiority of the defect engineered silicon. Microscopic aspects of damage effects are also discussed, including differences due to charged and neutral hadron irradiation.
The changes induced by neutron irradiation in n- and p-type silicon samples with starting resistivities from 10 /spl Omega/-cm up to 30 k/spl Omega/-cm, grown using different techniques, as ...float-zone (FZ), Czochralski (CZ) and epitaxial, have been analyzed by Van der Pauw and Hall effect measurements. Increasing the fluence, each set of samples evolves toward a quasi-intrinsic p-type material. This behavior has been explained in the frame of a two-level model, that considers the introduction during irradiation of mainly two defects. A deep acceptor and a deep donor, probably related to the divacancy and to the C/sub i/O/sub i/ complex, are placed in the upper and lower half of the forbidden gap, respectively. This simple model explains quantitatively the data on resistivity and Hall coefficient of each set of samples up to the fluence of /spl ap/10/sup 14/ n/cm/sup 2/.
Cryogenic semiconductor high-intensity radiation monitors Palmieri, V.G.; Bell, W.H.; Borer, K. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/2003, Letnik:
510, Številka:
1
Journal Article
Recenzirano
This paper describes a novel technique to monitor high-intensity particle beams by means of a semiconductor detector. It consists of cooling a semiconductor detector down to cryogenic temperature to ...suppress the thermally generated leakage current and to precisely measure the integrated ionization signal. It will be shown that such a device provides very good linearity and a dynamic range wider than is possible with existing techniques. Moreover, thanks to the Lazarus effect, extreme radiation hardness can be achieved providing in turn absolute intensity measurements against precise calibration of the device at low beam flux.
