It is shown that, in spite of the linearity of current-voltage characteristics of ionizing-radiation detectors based on semi-insulating GaAs compensated with Cr, the charge transport in these detectors is controlled by the barrier contacts at the anode and cathode. The anode contact is antiblocking for holes and behaves as an ohmic contact, whereas the cathode contact is blocking for electrons. This circumstance gives rise to the depletion of electrons in the active region under operating conditions. It is shown that this effect can bring about a decrease in the dark currents by a factor of 3 in comparison with the calculated value of the limiting current in a resistive structure based on semi-insulating gallium arsenide, which makes it possible to reduce the detector noise.

In activity the observed data of a life time of non-equilibrium charge carriers in detectors based on GaAs, compensated with Cr are shown. On the basis of the analysis of experimental data is established, that in electrical fields with strength in range from 1 to 10 kV/s the values of non-equilibrium electrons and holes life times do not depend on electric field strength. It is shown, that using of two miscellaneous techniques results in considerable difference in values of a nonequilibrium holes life time, while the life times of electrons have comparable values.

In the paper, studies of volt-ampere and volt-luxing characteristics of the detector structures based on gallium arsenide, compensated by chromium are carried out. It is shown that metallic contacts to a structure are barrier for electrons. One of contacts is inject at any bias polarity.

The growth of GaAs epitaxial structures for X- and gamma-ray detectors and the device characteristics have been investigated. Conditions of reproducible LPE growth of GaAs layers more than 100 mum thick on substrates of 40 mum 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 (10(7)-10(9))Omega cm and with thickness up to 550 mum.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 1 x 10(-7) A/cm(2) at a reverse bias voltage of 100 V.Alpha particle and gamma-ray spectra of the detectors have been measured. An X-ray image has been obtained with a strip detector based on LPE layers. (C) 2004 Elsevier B.V. All rights reserved.

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

Among prospect semiconductor materials for ionizing radiation detectors, GaAs looks very promising due to it 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 based on SI-GaAs are presented.

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.

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.

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 single quantum of electromagnetic radiation with energy E≥5keV, have high-speed response and radiation resistance and can be used for the development of high-efficiency multi-element detectors for modern diagnostic systems.

Results on the investigation of electrical characteristics of high-resistivity π-ν-n structures based on GaAs compensated with Cr and charge collection dependences on the average electric field and on detector structures parameters are presented.

Single and multi-element detectors for /spl gamma/-radiation (E/sub /spl gamma//>0.2 MeV) detection have been developed and investigated. Experimental results are in good agreement with calculation due to the high registration efficiency of the detector structure.

Single and multielements detectors for gamma-radiation (E-gamma > 0.2 MeV) detection have been developed and investigated. Experimental results are in good agreement with calculation due to high registration efficiency of the detector structure.

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 ∼ E13. 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.