N+GaAs subpicosecond photodetector irradiated by fast neutrons

We report experimental results of the characterization of an N⁺GaAs photodetector irradiated by fast neutrons with flux up to doses of 4×10¹⁷ n/cm² using a constructed electro-optic sampling system and illumination with 80-fs-wide laser pulses. The investigated N⁺GaAs sample was compared with the same non-irradiated sample. The device shows a response time of 680 fs full width at half maximum (648 GHz, 3-dB bandwidth) with a voltage amplitude of 3.1 mV. Changes in the shape of the electrical signal for different beam power excitations and bias voltages have been demonstrated. Using X-ray diffraction and diffuse scattering analyses, we have observed a decrease of the lattice constant and an almost three times decreased radius of nanoclusters; the density dislocations increased by over four times after neutron irradiation.