Evaluation of the diusion length in silicon diodes by means of the lateral IBIC technique E. Vittone a,b, * , F. Fizzotti a,b , E. Gargioni a,b , R. Lu a , P. Polesello b , A. LoGiudice a,b , C. Manfredotti a,b , S. Galassini c , M. Jaksic d a Dipartimento di Fisica Sperimentale, Universit  a di Torino, INFN-Sezione di Torino, via P. Giuria 1, 10125 Torino, Italy b INFM-Unit  a di Torino Universit  a, via P. Giuria 1, 10125 Torino, Italy c Facolt  a di Scienze, Universit  a di Verona, Strada Le Grazie, C  a Vignal, Borgo Roma, Verona, Italy d Ruder Boskovic Institute, Laboratory for nuclear microanalysis, P.O. Box 1016, 41001 Zagreb, Croatia Abstract The transport properties of silicon p  –n–n  diodes with a junction depth of about 47 lm have been investigated by means of the lateral IBIC technique. Cross section of the samples have been irradiated by a low intensity 5 MeV proton microbeam and the charge pulses have been recorded as a function of incident proton position. The charge collection eciency (cce) profiles show broad plateaux with values close to 100%. The region where the electric field is absent shows exponentially decreasing cce profiles. The estimate of the decay rate allows the diusion length of the minority carriers in the bulk of the device to be measured. The analytical method presented in this paper takes into account the dependence of the signal rise time on the incident proton position. The entire cce profile is in full agreement with the IBIC theory based on the extended RamoÕs theorem, which provides a very eective tool for quantitative estimates of transport parameters in semiconductor devices. Ó 1999 Elsevier Science B.V. All rights reserved. PACS: 72.20.Jv; 41.75.Ak Keywords: Silicon diodes; Electronic properties; Ion Beam induced charge; Diusion length 1. Introduction Ion beam induced charge IBIC is a widely used technique for the microscopical characterisation of semiconductor materials and devices [1–3]. Many of these measurements have been performed using ‘‘frontal geometry’’, i.e. by ion beam irradiation through the upper electrode of the sample under analysis. Since 1995, our group has developed a ‘‘lateral version’’ of the IBIC technique which consists in irradiating the cross section of a semi- conductor or insulator device in order to analyse the profiles of charge collection eciency (cce) from electrode to electrode [4–6]. Such a method permits an analysis of the transport properties of the carriers throughout the sample thickness and allows the electric field profile to be evaluated in fully depleted samples. Nuclear Instruments and Methods in Physics Research B 158 (1999) 476–480 www.elsevier.nl/locate/nimb * Corresponding author. Tel.: +39-0116707317; fax: +39- 116691104; e-mail: vittone@to.infn.it 0168-583X/99/$ - see front matter Ó 1999 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 8 - 5 8 3 X ( 9 9 ) 0 0 3 8 3 - 3