Influence of growing and doping methods on radiation hardness of n-Si irradiated by fast-pile neutrons

Silicon n-type samples with resistivity ~2.5*10³ Ohm*cm grown by the method of a floating-zone in vacuum (FZ), in argon tmosphere (Ar) and received by the method of transmutation doping (NTD) are investigated before and after irradiation by various doses of fastpile neutrons at room temperature. The radiation hardness of n-type silicon is shown to be determined first of all by the introduction rate of defect clusters and their parameters and then by the introduction rate of defects into the conducting n-Si matrix. The presence of oxygen, argon atoms and A-type defects (dislocation loops of the interstitial type) mainly increases the radiation hardness of n-Si. The effective concentration of carriers in irradiated silicon was calculated in the framework of Gossick's model taking into account the recharges of defects both in the conducting matrix of n-Si and in the space-charge regions of defect clusters. Grown by the method of the floating-zone melting in argon atmosphere the neutron-transmutation- doped silicon (NTD) has elevated radiation hardness. The introduction rate of divacancies in the conducting matrix of n-Si (NTD) is about five times less than in n-Si (FZ) and ~2 times less than in n-Si (Ar). The availability of the deformation strain field surrounding the argon-type impurities as well as A-type defects is supposed to promote the annihilation of divacancies with interstitial atoms of silicon

Semiconductor detectors for neutron flux measurements

Abstract Silicon detectors with 235U converter for neutron flux measurements over a wide energy range (from thermal up to epithemal neutrons) have been developed. The surface-barrier detectors with plastic converters were developed for fast neutron detection

Semiconductor sensors for dosimetry of epithermal neutrons

Minimum energy of neutron to displace atoms in silicon crystals are equal to 200 eV. Due to this fact testing our p-i-n diodes under irradiation by the epithermal neutrons was carried out. The more advanced p-i-n diodes on the base of high purity silicon were used at present work, and, as a result, we have obtained considerably more sensitive sensors for more wide range of neutron doses. The sensitivity of sensors is 0.14 V/Gy for average neutron energy of 24 keV

Silicon detectors for γ-ray and β-spectroscopy

Large active volume Si(Li) detectors were successfully developed for γ-ray spectrometry at room temperature that show a sufficient efficiency and an energy resolution that is better than scintillation detectors. The higher efficiency of the proposed detectors with respect to normal silicon diodes is achieved by increasing the active volume. For this purpose special attention is given to the selection of the initial material which has to show homogeneous electro-physical parameters, low concentration of oxygen impurities and high structural perfection. The technique of using lithium ions is used as these drift into large depths and hence the profile of the impurity distribution is optimized

Influence of preliminary irradiation on radiation hardness of silicon and indium antimonide.

Radiation hardness of semiconductor detectors based on silicon is, first of all, determined by an introduction rate of point defects and aggregation of defect clusters. So introduction of electrically inactive impurity of oxygen promotes taking a vacancy stream aside from a doping impurity of phosphorus. Thus, in spite of the greater capture radius of vacancies by phosphorus atoms, high concentration of oxygen will suppress formation of E-centres. Use of neutron transmutation doping method allows to receive silicon with enhanced radiation hardness. The preliminary irradiation with neutrons or charged particles with subsequent annealing also allows to increase radiation hardness of material. It is due to introduction into the volume of material some additional sinks for primary radiation defects that causes enhanced radiation hardness of such material

Influence of preliminary irradiation on radiation hardness of silicon and indium antimonide

Radiation hardness of semiconductor detectors based on silicon is, first of all, determined by an introduction rate of point defects and aggregation of defect clusters. So introduction of electrically inactive impurity of oxygen promotes taking a vacancy stream aside from a doping impurity of phosphorus. Thus, in spite of the greater capture radius of vacancies by phosphorus atoms, high concentration of oxygen will suppress formation of E-centres. Use of neutron transmutation doping method allows to receive silicon with enhanced radiation hardness. The preliminary irradiation with neutrons or charged particles with subsequent annealing also allows to increase radiation hardness of material. It is due to introduction into the volume of material some additional sinks for primary radiation defects that causes enhanced radiation hardness of such material

Study of Neutron Pre-Irradiated Silicon for Nuclear Detectors

The ways of increasing the radiation hardness of silicon were considered. It was then experimentally shown that a preliminary irradiation of the bulk silicon introduces sinks for radiation defects that leads to an increased radiation hardness of the silicon. Neutron transmutation doping of silicon can be considered as one form of preliminary radiation. It was shown that for neutron transmutated silicon the carrier removal rate in NTD after γ-irradiation is more than one order of magnitude smaller than in a standard reference specimen, but the carriers removal rate after neutron irradiation is approximately a factor of two less

Radiation hardness of silicon detectors based on pre-irradiated silicon

Radiation hardness of planar detectors processed from pre-irradiated and thermo-annealed n-type FZ silicon substrates, and standard FZ as a reference, was studied. The high purity n-Si wafers with carrier concentration 4.8x1011 cm-3 were pre-irradiated in Kiev’s nuclear research reactor by fast neutrons to fluence of about 1016 neutrons/cm2 and thermo-annealed at a temperature of about 850 1C. Silicon diodes were fabricated from standard and pre-irradiated silicon substrates by IRST (Italy). All diodes were subsequently irradiated by fast neutrons at Kiev and Ljubljana nuclear reactors. The dependence of the effective doping concentration as a function of fluence (Neff = f(F)) was measured for reference and pre-irradiated diodes. Pre-irradiation of silicon improves the radiation hardness by decreasing the acceptor introduction rate (b), thus mitigating the depletion voltage (Vdep) increase. In particular, b in reference samples is about 0.017 cm-1, and for pre-irradiated samples is about 0.008 cm-1. Therefore, the method of preliminary irradiation can be useful to increase the radiation hardness of silicon devices to be used as sensors or detectors in harsh radiation environments