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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. 

Epitaxial films of cubic boron nitride (c-BN) have been grown on single-crystal boron-doped diamond substrates by electron cyclotron resonance plasma-enhanced chemical vapor deposition using gas mixtures of Ar–He–N2–BF3–H2. The resulting c-BN films have been characterized using in situ x-ray photoelectron spectroscopy to establish the growth surface bonding (i.e., sp3 or sp2). The interface and film crystal structure were characterized with high resolution electron microscopy and electron-energy-loss spectroscopy. This study considers three stages of the growth process: in situ surface preparation, initial nucleation and growth of c-BN, and growth of the epitaxial c-BN layer. Prior studies from our group have established that hydrogen gas phase concentration affects fluorine-induced etching and c-BN nucleation. The results of this study establish that by optimizing the surface chemistry for all three stages of the growth process, it is possible to achieve an adherent, oriented epitaxial c-BN layer, a workable growth rate (∼50 nm/hr), cubic phase BN throughout, and negligible sp2 bonding except at the interface.