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

The transport properties of silicon p(+)-n-n(+) diodes with a junction dept h of about 47 mu m have been investigated by means of the lateral IBIC tech nique. 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 funct ion of incident proton position. The charge collection efficiency (cce) pro files show broad plateaux with values close to 100%. The region where the e lectric field is absent shows exponentially decreasing cce profiles. The es timate of the decay rate allows the diffusion length of the minority carrie rs in the bulk of the device to be measured. The analytical method presente d in this paper takes into account the dependence of the signal rise time o n 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. (C) 1999 Elsevier Science B.V. All rights reserved.