Development of semiconductor detectors for very harsh radiation environments in high energy physics applications

The Large Hadron Collider (LHC) at CERN has been designed to achieve the unprecedented luminosity of $10^{34} \rm{cm}^{-2} s^{-1}$. As a consequence, the silicon detectors close to the interaction region will receive severe doses of hadron irradiation. The present sensors are designed to survive fast hadron fluences of about $10^{15} \rm{cm}^{-2}$. Due to the anticipated radiation levels, the fluence expected at the innermost tracker detectors can already exceed this value before the end of the lifetime of the experiment, so that some experiments foresee to change these detectors after a few years of operation (e.g. LHCb VELO). Moreover, the option of increasing the luminosity of LHC to $10^{35} \rm{cm}^{-2} s^{-1}$ has been envisaged to extend the physics reach of the machine. An efficient tracking down to a few centimetres from the interaction point will be required to exploit the physics potential of the upgraded LHC. Under these conditions, the inner tracker detectors will need to survive fast hadron fluences above $10^{16} \rm{cm}^{-2}$. The CERN-RD50 project "Development of Radiation Hard Semiconductor Devices for Very High Luminosity Collider" has been set-up to explore detector technologies that will allow to operate devices up to, or beyond, this limit. The strategies followed by RD50 to enhance the radiation tolerance include the development of new or defect engineered detector materials (SiC, GaN, CZ and EPI silicon, oxygen enriched silicon), the evaluation of new detector designs (3D, Semi3D detectors), the improvement of present detector designs and, on the fundamental semiconductor physics aspect, the understanding of the microscopic defects causing the degradation of the irradiated detectors. The latest advancements within the RD50 collaboration will be reviewed and discussed in this work.