NEUTRON-IRRADIATION OF COLD GAAS DEVICES AND CIRCUITS MADE WITH AN ION-IMPLANTED MONOLITHIC PROCESS

We have irradiated with neutrons from SARA facility (Grenoble) four ve rsions of cryogenic GaAs monolithic preamplifiers and one MESFET at 87 K. The preamplifiers were designed to readout the ionization signal f rom the LAr electromagnetic calorimeter of ATLAS experiment. In this p aper, data on modification of preamplifier transfer function and degra dation of noise performance with irradiation are presented. New preamp lifiers (M- and D-versions) exhibited better resistance to irradiation than old C3 version, thanks to a better design of second stage. DC pe rformance of MESFET has been well characterized before and after irrad iation. Due to effects of carrier removal and mobility degradation, pi nch-off voltage V-p and maximum drain current I-dss dropped by factor 2.1 and 7.4, respectively, while the transconductance at standing curr ent I-d = 8 mA did not change after a fluence of about 13 x 10(14) neu trons/cm(2) (1 MeV equivalent).