Current injected detectors (CID) - a new approach for detector operation in very high radiation environment

For the upcoming Super LHC (SLHC) experiments on the LHC upgrade, Si detectors will still be considered as the main detectors for inner tracker. However, the radiation level in SLHC will be up to 10 times more than that in LHC due to the increase of luminosity from 10³⁴ cm^-2s^-1 to 10³⁵ cm^-2s^-1. In this study a new approach for radiation hard detectors based on the current injection in the detector bulk is considered. It is shown that the symmetric p⁺-n-p⁺ structures as well as regular p⁺-n-n⁺ silicon detectors after irradiation by neutrons up to 5middot10¹⁴ cm^-2 can operate at self-stabilized current injection (SSCI) or space charge limited current (SCLC) mode. This provides a stable electric field profile at any higher fluences with the electric field distributed in the entire detector thickness (full depletion mode). In this study operation of heavily irradiated Si detectors in the SSCI mode is confirmed by the measurements of I-V characteristics, which show the region with square I on V dependence and then the sharp current rise at a threshold voltage. It is shown that the threshold voltage rises linearly with the irradiation fluence that allows biasing the detectors by higher voltage with the fluence increase. This is obviously helpful for reduction of the collection time and consequently the related charge loss due to trapping.