Characterization of 150μm thick epitaxial silicon detectors from different producers after proton irradiation

Epitaxial (EPI) silicon has recently been investigated for the development of radiation tolerant detectors for future high-luminosity HEP experiments. A study of 150μm thick EPI silicon diodes irradiated with 24GeV/c protons up to a fluence of 3×1015p/cm2 has been performed by means of Charge Collection Efficiency (CCE) measurements, investigations with the Transient Current Technique (TCT) and standard CV/IVCV/IV characterizations. The aim of the work was to investigate the impact of radiation damage as well as the influence of the wafer processing on the material performance by comparing diodes from different manufacturers. The changes of CCE, full depletion voltage and leakage current as a function of fluence are reported. While the generation of leakage current due to irradiation is similar in all investigated series of detectors, a difference in the effective doping concentration can be observed after irradiation. In the CCE measurements an anomalous drop in performance was found even for diodes exposed to very low fluences (5×1013p/cm2) in all measured series. This result was confirmed for one series of diodes in TCT measurements with an infrared laser. TCT measurements with a red laser showed no type inversion up to fluences of 3×1015p/cm2 for n-type devices whereas p-type diodes undergo type inversion from p- to n-type for fluences higher than ≈2×1014p/cm2.