Assessment of SI GaAs particle detectors

Measurements of the charge collection efficiency (CCE) of radiation detectors fabricated from semi-insulating GaAs wafers have indicated that the CCE is reduced principally by trapping of electrons. Further measurements on wafers which have different thermal histories have been undertaken in order to identify the electron traps responsible for reducing the CCE of these devices. A correlation between CCE and electrical resistivity has been observed. Our data is consistent with a dominant dependence of CCE on the concentration of the ionized deep donor, EL2+.