1063-7826/04/3810- $26.00 © 2004 MAIK “Nauka/Interperiodica” 1187 Semiconductors, Vol. 38, No. 10, 2004, pp. 1187–1191. Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 38, No. 10, 2004, pp. 1223–1227. Original Russian Text Copyright © 2004 by Kalinina, Kholuyanov, Onushkin, Davydov, Strel’chuk, Konstantinov, Hallén, Nikiforov, Skuratov, Havancsak. 1. INTRODUCTION The ability of devices based on SiC to operate under extreme conditions (under high levels of radiation, at temperatures higher than 600°C, and in chemically active media) makes these devices useful in solving prob- lems related to space research, keeping record and control of nuclear materials and nuclear waste, and detecting high-energy nuclear particles. Taking into account the pos- sible wide range of applications of SiC-based devices, there is a need to study in more detail the effect of var- ious types of radiation on the processes of radiation- defect production in SiC. Such studies will make it pos- sible to affect the processes of controlled production or removal of various defect- and impurity-related centers in SiC in order to improve or intentionally vary the electrical properties of this material, as well as gain information about the radiation resistance of SiC. The data obtained in studying the effect of irradiation with α particles, neutrons, electrons, and protons on the nature of defects in SiC made it possible to clarify cer- tain special features of defect production in this mate- rial [1–4]. At the same time, study of the special fea- tures of defect production during irradiation of SiC with heavy high-energy ions (under conditions of a high level of ionization-related energy losses and a high rate of radiation-defect generation) has begun only recently [5–8]. In this paper, we report the results of comparative research into the effect of irradiation with fast neutrons and with 245-MeV Kr and 710-MeV Bi ions on defect production in lightly doped 4H-SiC epitaxial layers that had n-type conductivity and were grown by chemical vapor deposition (CVD). 2. EXPERIMENTAL We studied diode structures fabricated on the basis of 4H-SiC epitaxial layers that were grown by CVD and had a concentration of uncompensated donors of N d – N a = (5–8) × 10 15 cm –3 . The 26-μm-thick epitaxial layers were grown on commercial n + -4H-SiC substrates with N d – N a = 1 × 10 19 cm –3 . The p + –n–n + structures of the diode were formed using the implantation of 150-keV Al ions with a dose of 5 × 10 16 cm –2 with sub- sequent activation annealing for 15 s at 1700°C in an Ar atmosphere [9]. Ohmic contacts were formed using thermal vacuum sputtering–deposition of Al and Cr/Al onto the p + - and n + -type regions of the diode structures, respectively. In addition, we studied Schottky barriers with Al and Cr contact layers, which were also depos- ited thermally onto the epitaxial layers. Diode mesa structures with the Schottky barriers and p + –n junctions with an area of 1 × 10 –3 cm 2 and a height of 30 μm were formed using ion–plasma etching. The diode structures were subjected to various doses of irradiation with ELECTRONIC AND OPTICAL PROPERTIES OF SEMICONDUCTORS Optical and Electrical Properties of 4H-SiC Irradiated with Fast Neutrons and High-Energy Heavy Ions E. V. Kalinina 1 ^, G. F. Kholuyanov 1 , G. A. Onushkin 1 , D. V. Davydov 1 , A. M. Strel’chuk 1 , A. O. Konstantinov 2 , A. Hallén 3 , A. Yu. Nikiforov 4 , V. A. Skuratov 5 , and K. Havancsak 6 1 Ioffe Physicotechnical Institute, Russian Academy of Sciences, St. Petersburg, 194021 Russia ^e-mail: evk@pop.ioffe.rssi.ru 2 ACREO AB, Electrum 236, SE 16440 Kista, Sweden 3 Royal Institute of Technology (Department of Electronics), Electrum 229, SE 16440 Kista, Sweden 4 Specialized Electronic Systems, Moscow, 115409 Russia 5 Joint Institute for Nuclear Research, Dubna, 141980 Russia 6 Eötvös University, Pázmány P. sétány 1/A, H-1117 Budapest, Hungary Submitted March 1, 2004; accepted for publication March 23, 2004 Abstract—Photoluminescence and deep-level transient spectroscopy are used to study the effect of irradiation with fast neutrons and high-energy Kr (235 MeV) and Bi (710 MeV) ions on the optical and electrical properties of high-resistivity high-purity n-type 4H-SiC epitaxial layers grown by chemical vapor deposition. Electrical characteristics were studied using the barrier structures based on these epitaxial layers: Schottky barriers with Al and Cr contacts and p + –n–n + diodes fabricated by Al ion implantation. According to the experimental data obtained, neutrons and high-energy ions give rise to the same defect-related centers. The results show that, even for the extremely high ionization density (34 keV/nm) characteristic of Bi ions, the formation of the defect structure in SiC single crystals is governed by energy losses of particles due to elastic collisions. © 2004 MAIK “Nauka/Interperiodica”.