Paper 2003-03

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Radiation tolerance of epitaxial silicon carbide detectors for electrons, protons and gamma-rays

Nuclear Instruments and Methods in Physics Research A, 505, 3 (2003),645-655

F. Nava^a, E. Vittone^b, P. Vanni^c, G. Verzellesi^d, P.G. Fuochi^e, C. Lanzieri^f, M. Glaser^g

a. INFN and Dipartimento di Fisica, Università di Modena e Reggio Emilia, Via G. Campi 213/A, I-41100 Modena , Italy

b. Dipartimento di Fisica Sperimentale, Università di Torino, INFM-UniTo e INFN-To Italy

c. CNR-Istituto LAMEL, Bologna , Italy

d. INFM and DSI, Università di Modena e Reggio Emilia, Italy

e. CNR-Istituto ISOF, Bologna , Italy

f. Alenia Marconi Systems, Roma , Italy

g. CERN, Division EP TA1-SD, Geneve , Switzerland

Keywords: Radiation hardness; Device simulation; Silicon carbide; Semiconductor detectors and Charge–particle spectroscopy.

Abstract

Particles detectors were made using semiconductor epitaxial 4H-SiC as the detection medium. The investigated detectors are formed by Schottky contact (Au) on the epitaxial layer and an ohmic contact on the back side of 4H-SiC substrates with different micropipe densities from CREE. For radiation hardness studies, the detectors have been irradiated with protons (24 GeV/c) at a fluence of about 1014 cm-2 and with electrons (8.2 MeV) and g-rays (60Co source) at doses ranging from 0 to 40 Mrad. We present experimental data on the charge collection properties by using 5.48, 4.14 and 2.00 MeV a-particles impinging on the Schottky contact. Hundred percent Charge Collection Efficiency, CCE, is demonstrated for reverse voltages higher than the one needed to have a depletion region equal to the a-particle projected range, even after the irradiation at the highest dose.By comparing measured CCE values with the outcomes of drift-diffusion simulations, values are inferred for the hole lifetime, tp, within the neutral region of the charge carrier generation layer. tp was found to decrease with increasing radiation levels, ranging from 300 ns in non-irradiated detectors to 3ns in the most irradiated ones. The diffusion contribution of the minority charge carriers to CCE is pointed out..