Conclusions

The changes in reverse current and charge collection efficiency for SI-U GaAs detectors have been studied after irradiations with 1MeV neutrons, 24GeV/c protons and 300MeV/c pions. While the leakage current variations are slight and pose little problem to the operation of the detectors, the fall in cce gives major cause for concern. At a given high fluence, the reduction is greater for charged hadrons than for neutrons (this difference is discussed in detail in reference [9]). The cce falls rapidly in the first 3 $\times$ 10¹³ p($\pi$)/cm². The reduction has been shown to be due to both electrons and holes being trapped, with the hole mean free path affected much more dramatically. For an applied bias greater than V_fd the cce increases due to the increased signal from the electrons. Room temperature annealing has been identified in the reverse current characteristics and a slight improvement has also been seen in the cce. Annealing at elevated temperatures has shown beneficial effects in both leakage current and cce. The effect of proton irradiation on indium-doped GaAs detectors has shown the material to be no more radiation-hard than SI-U GaAs. Further tests on different samples should be performed.