Analysis of uniformity of as prepared and irradiated S.I. GaAs radiation detectors

The performance of GaAs unirradiated and proton irradiated detectors as a spectrometry devices has been tested by measuring the energy resolution for incident 2 MeV proton particles and the charge collection efficiency by microprobe technique IBIC (ion beam induced charge). The energy resolution improves with increasing the proton fluence at a given applied voltage, V_a, above the voltage V _d necessary to extend the electric field all the way to the ohmic contact and worsens with increasing V_a>V_d. On the contrary, in the unirradiated detectors the energy resolution improves with increasing V_a>V_d. IBIC spectra and IBIC space maps obtained by scanning a focused (8 μm²) 2 MeV proton microbeam on front (Schottky) and back (ohmic) contacts, support the observed electric field dependence of the energy resolution both in unirradiated and most irradiated detectors. The results obtained let us explain the effect of the electric field strength and the plasma on the energy resolution