Carbides heterostructures for a new generation of thermal neutron detectors – CADOR

CADOR project aims at developing a new generation of neutrons detectors (NDs) based on the highly stable carbide heterostructure boron carbide (BxC)/silicon carbide (SiC). In such devices, the few µm thick BxC layer will serve as thermal neutrons converter for the 4H-SiC based semiconductor detector. The high amount of 10B close to SiC detector should enhance the detection efficiency, allowing better performances for cleaning and dismantling operations, radioactive waste management and homeland security applications, or even for real-time ex-core nuclear power reactor monitoring. Two deposition methods of BxC layers will be used and compared for fabricating the NDs: physical vapor deposition (PVD) for amorphous to polycrystalline material and chemical vapor deposition (CVD) for polycrystalline to epitaxial one. In a first approach, amorphous to polycrystalline films from both methods will be used as the neutron-converter layers, deposited on top of a 4H-SiC p-n junction, for fabricating the simplest version of ND demonstrator (Demo1). Thanks to the recent mastering (by the project coordinator) of BxC epitaxy on 4H-SiC, a higher crystalline quality version of ND (Demo2) will be elaborated with an expected gain in terms of interface stability upon thermal stresses. A more innovating design to be investigated (Demo3) will take advantage of the intrinsic semiconducting properties of BxC material (which is known to be naturally p-type doped). It will involve a p-type epitaxial BxC film deposited on n- doped 4H-SiC in order to form the p-n junction. Chemical and mechanical stability of BxC/SiC interface up to 500°C will be studied as they are key requirements for all detector designs. Reaching these targets will require important material developments and characterizations for controlling the layers crystallinity, purity and intentional doping, as well as the different processing steps (dry etching, contacts…) for NDs fabrication. The fundamental electronic and optical properties of BxC material, which are largely unknown, will be determined. The different types of detectors will be simulated for both optimization of the designs and performance prediction. Selected demonstrators will be tested in a nuclear research facility for comparing their performances to the ones of actual reference detectors.