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

•Thermal neutron detection using (SI) GaAs and 4H-SiC semiconductor detectors.•6LiF conversion layer essential; its optimal thickness calculated using MCNPX code.•Calculated results supported by spectra measurement for different 6LiF thicknesses.•Similar response of (SI) GaAs and 4H-SiC detectors to thermal neutrons.•Two hills related to tritons (2.73 MeV) and α particles (2.05 MeV) identified.•Acceptable agreement between simulated and measured response obtained.•Comparison of detector materials discussed (operation conditions, costs, etc.).