  Using first principles calculations, this work investigates the suitability
of diamond/c-BN heterojunctions for high frequency, high power device
applications. The key quantities of band offsets and interface charge
polarization are examined for different crystallographic orientations [(110),
(111), or (100)], bond terminations (C-B or C-N), and substrates (diamond or
c-BN). The results indicate that both the (111) and (100) structures with polar
interfaces are likely to be a type-I alignment with the diamond conduction and
valence band extrema nested within the c-BN bandgap, whereas the non-polar
(110) counterpart may form type II as the valence band of c-BN is shifted down
substantially lower. The (111) and (100) structures also show net charge
polarization in a narrow region at the interface. The electron-deficient and
electron-rich nature of the C-B and C-N bonding are found to induce charge
redistribution leading to an essentially 2D sheet of negative and positive
polarization. With the predicted band alignments suitable for carrier
confinement as well as the possibility of the modulation and polarization
doping, the diamond/c-BN heterostructures are a promising candidate for
high-performance electronic devices with a highly conductive 2D channel. Both
p-type and n-type devices appear possible with a judicious choice of the
heterojunction configuration.
