Study on 150μm thick n- and p-type epitaxial silicon sensors irradiated with 24 GeV/c protons and 1 MeV neutrons

A study on 150μm epitaxial (EPI) n- and p-type silicon diodes irradiated with neutrons up to 8×1015n/cm2 and protons up to 1.7×1015p/cm2 has been performed by means of CV/IV, charge collection efficiency (CCE) and transient current technique (TCT) measurements. It is found that the effective space charge density increases three times faster after proton than after neutron irradiation with a slightly higher effective space charge generation rate for n-type material compared to p-type material. A drop in charge collection efficiency already at fluences of 1×1012neq/cm2 can be seen in n-type material, but is absent in p-type material. TCT measurements show space charge sign inversion from positive to negative charge in n-type material after neutron irradiation and from negative to positive space charge in p-type material after proton irradiation. No difference was found in the response of diodes manufactured by different producers out of the same wafer material.