Measurements of charge collection profiles in virgin and strongly irradiated silicon diodes by means of the micro IBICC technique

Ion Beam Induced Charge Collection (IBICC) method is a very sensitive technique to investigate the electronic features of semiconductor materials and devices. This technique consists in measuring the charge induced at the electrode by the motion of free carriers generated by a spatially scanned focused energetic ion beam. The measurement of the charge collection efficiency as a function of the ion impact position allows the electronic features of semiconductor materials and devices to be mapped. We used the microbeam facility of the Ruder Boskovic Institute in Zagreb (HR) to perform lateral IBICC measurements of virgin, Au doped and strongly irradiated (frontal irradiation with 6.5 MeV He++ ions for a total dose of 2E12 ion/cm2) p+/n/n+ silicon diodes in order to evaluate charge collection profiles (CCP) under different applied bias conditions. Basic transport parameters (minority carrier diffusion length, depletion region width) have been extracted from the experimental profiles by using a mathematical procedure based on the extended Ramo's theorem. The irradiated sample shows charge collection profiles strongly influenced by the radiation damage as evidenced by a drop of charge collection efficiency which occurs at the end of the He++ ion penetration range.