[en] The growth of GaAs epitaxial structures for X- and γ-ray detectors and the device characteristics have been investigated. Conditions of reproducible LPE growth of GaAs layers more than 100 μm thick on substrates of 40 μm diameter have been established. Complex doping with tin and deep Cr-acceptor have been studied for the liquid-phase epitaxial growth in a wide temperature range. A method has been developed for GaAs:Sn,Cr layer growth with the resistivity in the range (10⁷-10⁹)Ω cm and with thickness up to 550 μm. Detector p-i-n structures have been fabricated on the base of high-resistivity GaAs layers. The electric field distribution and current flow mechanisms in the diodes have been studied. Diodes have been fabricated with a dark current density of 1x10^-7A/cm² at a reverse bias voltage of 100 V. Alpha particle and γ-ray spectra of the detectors have been measured. An X-ray image has been obtained with a strip detector based on LPE layers

[en] We present first results obtained with pad detectors processed from 3 inch diameter GaAs wafers compensated with Cr. The detector characteristics are analyzed from the point of view of uniformity across the wafer

[en] Among the possible semiconductor materials for ionizing radiation detectors, GaAs looks very promising due to its high carrier mobility, wide band gap and high density. A comparative analysis of physical and electrical characteristics of GaAs semi-insulating layers (SI-GaAs) fabricated by means of different technological methods is given in this work. The main parameters of detector structures and multi-element detectors on the base of SI-GaAs are presented

[en] The article presents results of investigation of interaction of the structures based on GaAs compensated by interaction of the deep centers with ionizing radiation of a wide spectral range. The structures are able to record a single quantum of electromagnetic radiation with energy E≥5 keV, have high-speed response and radiation resistance and can be used for the development of high-efficiency multi-element detectors for modern diagnostic systems

[en] Unlike conventional GaAs detector structures that use a space charge region (SCR) of a barrier structure, we propose to form a detector structure of resistor type made of GaAs compensated with Cr. In this case, the electric field distribution, ξ(x), is not screened by the ion concentration in the SCR but it is defined only by the uniformity of the distribution of the resistance value in the structure. The experimental results on measurements of the electrophysical characteristics and the electric field distribution are presented. It is shown that in these structures the electric field distribution is uniform through the whole high-resistive layer with a thickness up to 1 mm. The possibility of achieving high values of charge collection efficiency of gamma-radiation is demonstrated

[en] Unlike conventional GaAs detector structures, which operation is based on the use of a space charge region of a barrier structure, we propose to form a detector structure of resistor type. In this case, the electric field distribution, ξ(x), is not screened by the ion concentration in the SCR but it is defined only by the uniformity of the resistance value distribution in the structure. The experimental results on charge collection efficiency for the detector irradiation with α, β, γ-radiation are presented. It is shown that the amplitude spectrum shape in the case of interaction with γ-radiation is defined mainly by the electron component of the charge. The simulation of the detector response function confirms it. It is established that, despite of hole trapping, it is possible to achieve high values of charge collection efficiency of γ-radiation. Explanation of the charge collection efficiency dependence on a type of ionizing radiation is made. Problems of design of the detector with high charge collection efficiency and low dark current are discussed

[en] A comparative analysis of characteristics of detector structures fabricated by means of technology of epitaxial growth of an undoped high-resistive GaAs layer as well as structures based on SI-GaAs compensated with Cr during a diffusion process is presented in this work. Advantages and disadvantages of the proposed methods of formation of high-resistive layers, their electrophysical characteristics and properties are examined. Limit parameters of the detector structures which can be achieved by using a combination of technological methods are analyzed

[en] GaAs structures with deep centres have been proposed for the manufacture of microstrip detectors (MSD). It has been shown that the processes of collection of non-equilibrium charge carriers can be described by applying the drift model in which the dependence of the amplitude of the registered charge on the electric field, E, is approximately Q∝E^1/3. The main region responsible for charge collection is the space charge region of the π-ν junction and the high resistivity π region within the n⁺-π-ν-n structures fabricated by in-diffusion of Cr and Fe deep dopants into substrate GaAs wafers. (orig.)

[en] High resistivity π-ν-n structures are shown to differ significantly from traditional drift detectors. It has been found that the amount of charge formed by a minimum ionizing particle (mip) in these structures does not depend on the bias. We consider this phenomenon to be associated with the relaxation properties of these structures because τ_d >>τ₀. (orig.)

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