Performance of a GaAs microstrip detector in a test beam experiment

A commercially produced gallium arsenide microstrip detector has been tested in a 100 GeV electron/pion beam. The detector has a 50 μm pitch on a 200 μm thick substrate. The signal-to-noise ratio was 13-to-1 at the maximum voltage of 180 V and the detection efficiency was better than 99%. The charge-collection efficiency was estimated to be 41% corresponding to a collected charge of 10 600e. The spatial resolution was found to approach the expectation of ≈ pitch SN. There is some evidence for an unusual charge sharing which may be due to trapping.