Comparison of semi-insulating GaAs and 4H-SiC-based semiconductor detectors covered by LiF film for thermal neutron detection

In this contribution we have focused on comparison of spectroscopic properties of semi-insulating (SI) GaAs and 4H-SiC detectors of thermal neutrons fabricated at the Institute of Electrical Engineering SAS in Piestany. (LiF)-Li-6 reactive film has been applied on Schottky contact as a convertor of thermal neutrons to detectable charged particles (tritons and a particles). Optimal thickness of the (LiF)-Li-6 film has been determined for front side irradiation using MCNPX code to be ca 25 mu m. From the energies deposited by secondary charged particles in the active volume of a detector, corresponding responses have been calculated for different thicknesses of the (LiF)-Li-6 conversion layer. The calculated responses have been compared with those collected by measurements using thermal neutrons generated by Pu-239-Be neutron source. Thermal neutron spectra have been recorded by SI GaAs and 4H-SiC detectors using different (LiF)-Li-6 film thicknesses. Generally, in spite of limited spectroscopic performances of the studied detectors, two hills related to tritons (2.73 MeV) and a particles (2.05 MeV) are discernible in all spectra beside a noise peak positioned in the low energy region. The specific differences between SI GaAs and 4H-SiC detector response to thermal neutrons will be closely discussed in the paper.