  Cubic boron nitride (cBN) is an ultra-wide bandgap, super-hard material with
potential for extreme-temperature and -pressure applications. A
proof-of-principle p-n junction using cBN was demonstrated almost three decades
ago. However, to date, there remain two unresolved challenges that prevent its
practical use in technologies: (i) it is difficult to produce high-quality cBN
films and (ii) it is difficult to controllably n- and p-dope its matrix. In
this theoretical work, we study the reasons for doping-limitations, which is an
acute issue in realizing cBN-based electronics. In particular, we find that
different unintentionally-present intrinsic and extrinsic defects act as
compensating defects and/or introduce trap states. In turn, the presence of
these defects and their complexes affect the incorporation, as well as the
electronic structure properties, of shallow dopants [silicon and beryllium],
which are introduced intentionally to n- and p-dope cBN. Our analysis of
doping-limitations provides a path towards finding solutions for controllably
n- and p-doping cBN.
