Band offset between cubic boron nitride and nitrogen-plasma terminated boron-doped diamond (111)

Diamond electronics has attracted attention for high power and high frequency device applications. Cubic boron nitride (c-BN) may be considered as a suitable dielectric layer for electron channel diamond metal–insulator–semiconductor field effect transistors (MISFETs) provided that its valence band edge can be positioned above that of diamond. This study reports experimental measurement of the valence band offset (VBO) between c-BN and nitrogen-plasma terminated boron-doped diamond (111). Nitrogen plasma processing was used to produce C–N bonding at the diamond surface. Electron cyclotron resonance plasma enhanced chemical vapor deposition was then used to deposit epitaxial c-BN films on the N-terminated diamond substrate, as confirmed by cross-sectional high-resolution electron microscopy. X-ray and ultraviolet photoemission spectroscopies indicated that the valence band maximum of c-BN is positioned 0.4 eV above that of diamond resulting in a type II staggered band alignment. This result is consistent with theoretical predictions of the VBO between the two materials in the (111) surface orientation, indicating that c-BN with C–N interface bonding can be used as a dielectric layer for electron channel diamond (111) MISFET devices.