50 IEEE TRANSACTIONS ON MAGNETICS, VOL. 49, NO. 1, JANUARY 2013 Prospects of Using In-Containing Semiconductor Materials in Magnetic Field Sensors for Thermonuclear Reactor Magnetic Diagnostics Inessa Bolshakova , Ivan Vasilevskii , Ladislav Viererbl , Ivan Ďuran , Nelli Kovalyova , Karel Kovarik , Yaroslav Kost , Olena Makido , Jana Sentkerestiová , Agata Shtabalyuk , and Fedir Shurygin Magnetic Sensor Laboratory, Lviv Polytechnic National University, Lviv, Ukraine National Research Nuclear University “MEPhI”, Moscow, Russia Research Centre Rež, Husinec–Rež, Czech Republic Institute of Plasma Physics AS CR, Association EURATOM-IPP.CR Praha, Czech Republic Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague, Prague, Czech Republic The work presents the results of experimental investigation into the effect of neutron irradiation on thin-ﬁlm magnetic ﬁeld Hall sensors. It is shown that sensors based on InSb/i-GaAs heterostructures are promising for application under radiation conditions in thermonuclear reactor magnetic diagnostics systems. At the same time, the presence of buffer layers in InAs/i-GaAs heterostructures makes this material unﬁt for application under neutron ﬂux conditions. Index Terms—III-V semiconductor materials, magnetic sensors, neutron radiation effects, radiation-resistant Hall sensors. I. INTRODUCTION O NE of the possible ways to solve the task of increasing the accuracy of steady-state magnetic ﬁeld measurements in thermonuclear reactors under long-pulse plasma burning is to use semiconducting Hall sensors, as they are capable of mea- suring steady-state and rapidly changing magnetic ﬁelds alike with high precision and high resolution [1]. However, the use of semiconducting sensors in thermonuclear reactors imposes requirements to their parameter stability in radiation and tem- perature conditions of such facilities. InSb, InAs, GaAs, and Si are the semiconducting materials most commonly used for Hall sensors of magnetic ﬁeld. How- ever, due to the features of their band structure Si and GaAs rapidly develop high resistance under the inﬂuence of irradia- tion and are therefore not ﬁt for sensor production. Experimental and theoretical research experience has shown [2]–[4] that In-containing semiconducting compounds of InSb and InAs, given certain technological conditions of their pro- duction, are the most prospective materials for developing sen- sors that are operable under severe radiation conditions. Nevertheless, the behavior of these materials in irradiation environment differs, which is also associated with the features of their band structure. The accumulation of radiation defects leads to the change of Fermi level location, which moves from its initial position to the boundary position , and thus serves as the main underlying reason for changes in the semi- conductor’s electrophysical properties under irradiation [5]. Current approach to ensuring the radiation resistance of semi- conductor materials and their based devices involves ﬁrst of all determining the relation between radiation-induced changes in semiconductor material characteristics and basic crystal param- eters. Such approach makes it possible to predict the direction Manuscript received July 11, 2012; accepted August 27, 2012. Date of current version December 19, 2012. Corresponding author: I. Ďuran (e-mail: duran@ipp.cas.cz). Color versions of one or more of the ﬁgures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identiﬁer 10.1109/TMAG.2012.2217482 of the changes of semiconductor’s electrophysical properties which are expected to take place under the effect of radiation, as well as allows using the level of doping and the choice of doping impurities to ensure the material’s resistance to high- energy irradiation. Radiation-induced parameter changes of the studied mate- rials—InSb, InAs and their based sensors—depend on several factors, irradiation conditions being the crucial ones: the energy spectrum of accelerated particles, received ﬂuence, and irradi- ation temperature most notably; along with initial parameters of the material—primarily initial concentration of free charge carriers. The effect of these factors has been analyzed on the basis of a signiﬁcant number of experimental data obtained while irradiating thin-ﬁlm sensors based on heterostructures without intermediate buffer layers and on heterostructures with intermediate buffer layers of and with reactor neutrons and high-energy electrons. The experiments were conducted using the on-line investiga- tion method, where sensor parameters are measured in real-time mode during their irradiation in nuclear reactor channel. The ex- periments involved using instrumentation that was developed in the Magnetic Sensor Laboratory and includes rigs for placing sensors under study into reactor channel, magnetic ﬁeld source, control electronics, transmission lines and software. (Fig. 1) [6]. II. STUDYING InSb/i-GaAS HETEROSTRUCTURES The effect of reactor neutron irradiation has been studied on InSb/i-GaAs samples in the channels of nuclear research reactors: IBR-2 (Joint Institute for Nuclear Research, Dubna, Russia), WWR-M (Petersburg Nuclear Physics Institute, Gatchina, Russia) and LVR-15 (Nuclear Research Institute, Rež, Czech Republic). Each of these reactors has a dif- ferent ratio between thermal and fast neutrons in ﬂux—0.25, 10.1 and 18.4 respectively. The effect of irradia- tion conditions on the parameters of thin-ﬁlm magnetic ﬁeld sensors was determined on the basis of the magnitude of their 0018-9464/$31.00 © 2012 IEEE