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 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.