Radiation Physics Research

Silicon is a material of choice for the fabrication of detectors that are used in high-energy physics experiments. These detectors are, however, damaged by the same radiation they are meant to detect.  Radiation generates defect levels in the energy gap of the material that are responsible for change in electrical properties of the detector. Changes in electrical properties make the detector to operate inefficiently. As a result, the detectors are unstable and hence cannot be reliable when operating continuously under harsh conditions.

The radiation damage is responsible for an increase in leakage current and in full depletion voltage of the detectors. The detectors have been found to be conductivity type inverted after the damage. The damage is also responsible for a negative capacitance in forward bias and a low-voltage peak in reverse bias of the detector. The results of these parameters have not been fully understood. Thus, the effects of radiation on silicon devices still need to be further studied to improve radiation-hardness of the detectors. To improve radiation hardness of silicon it has been found that the material must be defect engineered before fabrication of the detector.

Defect engineering allows controlled modification of electronic properties of defects in comfortable manner so that the favourable properties of the material are improved while the unfavourable ones are minimized. In silicon gold and platinum generate defects that are responsible for suppression of radiation effects. Thus, doping silicon with these metals is a promising strategy to improve radiation-hardness of the material.  The metals are, however, expensive, and not easily available for research purposes.  Depending on the amount and the doping method, these metals can also exhibit similar properties as those of irradiation.  It is also important that the effects of other metal impurities on electrical properties of silicon detectors be investigated to replace the expensive ones.