<i>In-Situ</i>Study of Non-Equilibrium Charge Carriers’ Behavior under Ultra-Short Pulsed Electrons Irradiation in Silicon Crystal

The recombination processes for charge carriers have been studied in n-type silicon crystals which were irradiated by pico-second duration pulse electrons with energy of 3.5 MeV (ultrafast irradiation), and maximum dose of 3.3 × 1013 el/cm2. In-situ measurements were carried out under artificial conditions simulating natural environment (space, semiconductor detectors, etc.). The observed phenomena were investigated experimentally in-situ using a high-speed oscilloscope equipped with a special preamplifier. Following irradiation to particular doses, some peculiarities of the recovery time of the semiconductor equilibrium condition (“characteristic time”), were obtained. Thus, it was found that the value of the “characteristic time” differs by an order of magnitude from the lifetime of the non-equilibrium (minority) charge carrier measured in an ex-situ regime. However, their behavior, as a function of irradiation dose, is similar and decreases with dose increase. Investigations of the dependencies of electro-physical parameters on irradiation dose, using Hall effect measurements, showed that at particular doses the radiation defects thus created, have an insignificant influence on the concentration of the charge carriers, but change their scattering properties appreciably, which affects the time parameters for the recombination of the semiconductor charge carriers. This investigation uses a novel approach to solid-state radiation physics, where in situ measurements were conducted in addition to conventional pre- and post-irradiation.

In-Situ Study of Silicon Single Crystals Conductivity under Electron Irradiation

The influence of electron radiation on the properties of semiconducting silicon single crystals (Si)—both n- and p-types (currently one of the most widely applied material in the electronic technology) was studied under the electron irradiation process in-situ in air (in common conditions). Higher value of electro-conductivity (σ) during the irradiation process with respect to after irradiation was observed, which was explained by ionization and capture mechanisms resulting in the formation of non-equilibrium carriers (hole-electron pairs). The kinetics of radiation defects generation, their physical nature, temperature stability and relaxation are examined. Structural radiation defects formation: point and complexes, their influence on the silicon conductivity are considered.

The Influence of Pico-Second Pulse Electron Irradiation on the Electrical-Physical Properties of Silicon Crystals

The studies of the influence of pico-second (4 × 10-13 sec.) pulse electron irradiation with energy of 3.5 MeV on the electrical-physical properties of silicon crystals (n-Si) are presented. It is shown that in spite of relatively low electron irradiation energy, induced radiation defects are of cluster type. The behavior of main carrier mobility depending on temperature and irradiation dose is analyzed and charge carriers’ scattering mechanisms are clarified: on ionized impurities, on point radiation defects with transition into cluster formation. Dose dependencies of electrical conductivity and carrier mobility for samples of various specific resistivities are given.

The Interaction of Impurity Oxygen with Radiation Defects in Silicon Crystal

Present paper describes the investigation of vacancy (V) and interstitial (I) annihilation on oxygen atoms by means of infrared (IR) absorption and Hall-effect measurements of the accumulation of vacancy-oxygen complexes (VO) in Si crystals at high energy electron irradiation. Silicon samples, containing along with isolated oxygen atoms, more complicated oxygen quasi-molecules of SiOn (n = 1, 2, 3…) type, were used. At isochronal and isothermal annealing in the temperature range of 300°C - 350°C, apart from the reaction of vacancy capturing by oxygen atoms with formation of A-centers, more complicated reactions with participation of vacancies and oxygen atoms were observed: A-centers, oxygen containing quasi-molecules. A model is suggested to describe the observed processes that are qualitatively different from those taking place in samples containing completely dissociated oxygen.

Quasi-Chemical Reactions in Irradiated Silicon Crystals with Regard to Ultrafast Irradiation

This paper reports results from an investigation of the interaction of displaced Si-self atoms (I) and their vacancies (V), with impurities in crystalline silicon (Si), as induced by micro-second pulse duration irradiation with electrons at different energies: 3.5, 14, 25 and 50 MeV and pico-second pulse duration with energy 3.5 MeV. V-V, I-impurity atom and V-impurity atom interactions are analyzed both experimentally and as modeled using computer simulations. A process of divacancy (V2) accumulation in the dose-dependent linear region is investigated. The effect of impurities on recombination of correlated divacancies, and I-atoms that had become displaced from regular lattice points is estimated by computer modeling of an appropriate diffusion-controlled process. It is concluded that the experimental results can be interpreted quantitatively in terms of a strongly anisotropic quasi-one-dimensional diffusion of displaced I-atoms. In addition, a significant difference is found between the effects of pico-second duration electron beam irradiation, which causes the formation of A-centre (V + Oxygen) clusters, while when the beam is applied on a micro-second timescale, divacancies are created instead, although the electrons have the same energy in both cases.

Scattering of Conduction Electrons on the Static Deformation Raised by Irradiation in n-GaP Crystals

Study of spectral dependences of absorption coefficient at the region of absorption by free carriers shows that the introduction of radiation defects in n-GaP crystals leads to the appearance of additional scattering besides of traditional ones. A new scattering mechanism on “frozen” phonons (deformation localized near the radiation defects) is suggested and its behavior in experimental and theoretical aspects taking into account Х1с-Х3с transitions at the scattering process has been studied. It was shown that the increase of “frozen” phonons’ concentration results to the growth of this mechanism contribution in the whole scattering and the absorption coefficient by free carriers is described approximately by low α ~ ω-r, where -1/2 ≤ r ≤ 7/2. Suggested scattering mechanism allows explaining qualitatively the decrease of r. It was established that the dis- ordered by irradiation region effectively decreases the concentration of free carriers, but being a region of increased resistivity, it influences the scattering slightly even at the actual quantum region .