Ni doping of semiconducting boron carbide

Semiconducting boron carbide (BC) is intrinsically p-type. The addition of Ni has been shown to dope it n-type. I-V measurements on Ni doped BC on both p-and n-type Si (1*10$^{15}$ cm$^{-3}$ and 4.5*10$^{13}$ cm$^{-3})$ indicate changes in the doping level with increasing Ni concentration. At the highest dopant level, Ni doped BC on n-type Si showed n-n+ diode characteristics. The change of doping concentration was confirmed by the built-in potential increase from 0.1 V in the low Ni doped p-n diode to 1.2 V in the high Ni-doped p-n diode as well as by measurements of the reverse saturation current. The addition of Ni does not lead to significant structural changes in the BC as measured by x-ray diffraction. X-ray fluorescence data indicate an upper bound of 2 ppm for the Ni concentration. Using these results homojunction p-n diodes were fabricated from layers of undoped p-type BC and Ni doped n-type BC and characterized by I-V and capacitance-voltage (C-V) measurement. Homojunction devices are shown to be especially promising for thermal neutron detection.