Radiation-induced modification of trap occupancy in polycrystalline diamond detectors

Metal–semiconductor–metal (MSM) diamond structures are investigated for radiation detection in the UV and X-ray spectral range. Several priming procedures by UV or X-ray irradiation are carried out in order to overcome device performance limitations related to the film polycrystalline structure. Sub-bandgap spectral responses monitored after different priming steps by UV laser pulses or X-ray beams exhibit a modification of trap occupancy, particularly in the 1–3 eV energy range. These variations appear responsible for both an increase of the minority carrier lifetime product and a radiation-induced barrier lowering, as deduced by photoelectric characteristics modeling.