Behavior of epitaxial GaAs layers as α particle detectors

The properties of epitaxial GaAs-based p(+)-n structures used as light-ion (alpha particle) were studied. A comparison is made with the latest published data on the possibilities of present-day semi-insulating GaAs (SI-GaAs). It is noted that the content of impurities and structural defects forming deep levels in the band gap of the material is two orders of magnitude lower in epitaxial layers. The deep levels determine the conditions of transport of nonequilibrium carriers in the detector, allowing for trapping of the carriers, and they also determine the electric-field profile. The charge-carrier lifetime was found to be greater than or equal to 200 ns. This is two orders of magnitude longer than the values for SI-GaAs, in complete agreement with the lower content of deep centers. It is shown how deep centers influence the field profile, forming a quite large region of low field values. (C) 1998 American Institute of Physics. [S1063-7850(98)00204-3].