Indium doped samples

 

Two detectors were fabricated with 500$\mu$m thick SI GaAs doped with indium [5]. These were tested before and after an exposure of 1.4 $\times$ 10¹⁴ 24GeV/c protons/cm². The reverse current of the detectors before irradiation was 30nA/mm², less than for the 500$\mu$m thick SI-U GaAs detectors. After the irradiation the value of V_fd was reduced to only 220V, compared to 340V for the undoped sample. The current at the applied bias of V_fd was 0.4$\mu$A (57nA/mm²) which was higher than that of the undoped sample which was 0.22$\mu$A. The charge collection efficiency for the indium doped samples was less that that of the undoped samples before irradiation by 20%. After the irradiation the signal fell to 10% (6650 electrons) compared to 17% (11305 electrons), respectively, for an applied bias of 1000V.