No abstract

No abstract

No abstract

In this work we fabricated detectors based on semi-insulating GaAs and studied their electrical properties (current-voltage characteristics, galvanomagnetic measurements) after irradiation with 5 MeV electrons from a linear accelerator up to a dose of 104 kGy. A series of detectors were prepared using Ti/Pt/Au Schottky contact with 1 mm diameter. The thickness of the base material was about 230 µm. A whole area Ni/AuGe/Au ohmic contact was evaporated on the back side. For galvanomagnetic measurements we used three samples from the same wafer. All samples were irradiated by a pulse beam of 5 MeV electrons using the linear accelerator in 11 steps, where the accumulative dose increased from 1 kGy up to 104 kGy. Also different dose rates (20, 40 and 80 kGy/h) were applied to the samples. After each irradiation step we performed electrical measurement of each sample. We analyze the electron Hall mobility, resistivity, electron Hall concentration, breakdown voltage and reverse current of samples before and after irradiation using different dose rates. K: Radiation damage to detector materials (solid state); Solid state detectors; Materials for solid-state detectors 1Corresponding author.

and the Slovak Academy of Sciences No. VEGA-2/0062/13 and No. VEGA-2/0175/13. MOTIVATION  Bulk Semi-Insulating (SI) GaAs: suitable material for preparation of high-energy charged particle detectors, gamma ray detectors as well as the neutron detectors.

The radiation hardness of Semi-Insulating (SI) GaAs detectors against 5 MeV electrons is investigated in this paper. The influence of two parameters, the accumulative absorbed dose (from 1 to 120 kGy) and the applied dose rate (20, 40 or 80 kGy/h), on detector spectrometric properties was studied. The electron irradiation has negatively affected the detector CCE (Charge Collection Efficiency). Un-irradiated detectors exhibited the CCE of 79% at maximum operating reverse voltage of 300 V and reached the maximum CCE of 51% at 200 V after irradiation by a dose of 120 kGy. Relative energy resolution was also affected by electron irradiation. Its global degradation was observed in the range of doses from 24 up to 120 kGy, where an increase from 19% up to 39% at 200 V reverse voltage was noticed. On the other hand, a global increase of detection efficiency with dose, by about 30% at 120 kGy, was observed with all samples. We did not observe any significant influence of chosen dose rates applied during irradiation on investigated spectrometric properties of detectors.

We fabricated and characterized 4H-SiC Schottky diodes as a spectrometric detector of alpha particles. A thin blocking contact of Ni/Au (15 nm) was used to minimize the influence on alpha particles energy. Current-voltage characteristics of the detector were measured and a low current density below 0.3 nAcm −2 was observed at room temperature. 239 Pu 241 Am 244 Cm was used as a source of alpha particles within the energy range between 5.1 MeV and 5.8 MeV for detector testing. The charge collection efficiency close to 100 % at reverse bias exceeding 50 V was determined. The best spectrometric performance shows a pulse height spectrum at a reverse bias of 200 V giving an energy resolution of 0.25 % in the full width and half maximum for 5.486 MeV of 241 Am.

Semi-insulating (SI) GaAs detectors were irradiated by 5 MeV electrons up to a dose of 69 kGy, in order to test their radiation hardness. The electric and spectrometric stability of detectors was examined as a function of the absorbed dose. Investigated detectors showed a very good detector radiation resistance within a dose up to 40 kGy followed by deterioration of some spectrometric and electric properties. However, the reverse current and the detector charge collection efficiency showed minimum changes with the overall applied doses. The obtained results will be used as a preliminary study for further radiation-hardness investigations of GaAs detectors against high energy electrons. This will complete our previous studies of GaAs detector radiation hardness against fast neutrons and γ-rays.