Paper 99-13

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Evaluation of the diffusion length in silicon diodes by means of the lateral IBIC technique.

Submitted at 6th Int. Conf. on Nuclear Microprobe Technology and Applications, Spier Estate, South Africa, 11-16 October 1998, and Nuclear Instruments and Methods in Physics Research B 158 (1999) 476-480.

E.Vittone1,2 ,F.Fizzotti1,2, R.Lu1, P.Polesello2, A.LoGiudice1,2, C.Manfredotti1,2, S.Galassini3 , M.Jaksic4

1Dipartimento Fisica Sperim., Università di Torino, INFN-Sez. di Torino, via P.Giuria 1, 10125 Torino (I)

2INFM- Unità di Torino Università, via P.Giuria 1, 10125 Torino (I)

3Facoltà di Scienze, Università di Verona, Strada Le Grazie, Cà Vignal, Borgo Roma, Verona (I)

4Ruder Boskovic Institute, Lab. for nuclear microanalysis,P.O.Box 1016, 41001, Zagreb (HR)


Keywords: Silicon diodes, Electronic properties , Ion Beam Induced Charge , Diffusion Length


The transport properties of silicon p+-n-n+ diodes with a junction depth of about 47 m m 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 efficiency profiles show broad plateaux with values close to 100%.

The region where the electric field is absent shows exponentially decreasing charge collection efficiency profiles. The estimate of the decay rate allows the diffusion 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 Ramo’s theorem, which provides a very effective tool for quantitative estimates of transport parameters in semiconductor devices.