Comparison of radiation hardness of P-in-N, N-in-N, and N-in-P silicon pad detectors

The very high radiation fluence expected at LHC (Large Hadron Collider) at CERN will induce serious changes in the electrical properties of the silicon detectors that will be used in the internal layers of the experiments (ATLAS, CMS, LHCb). To understand the influence of the fabrication technology in the radiation-induced degradation, silicon detectors were fabricated simultaneously with the three different possible technologies, P-in-N, N-in-N, and N-in-P, on standard and oxygenated float-zone silicon wafers. The diodes were irradiated with protons to fluences up to 10¹⁵ cm^-2. The measurements of the electrical characteristics, current-voltage and capacitance-voltage, are presented for the detectors manufactured with the three technologies. In terms of alpha factor (leakage current) the three technologies behave similarly. In terms of beta factor (effective doping concentration) N-in-P devices show the best performances.