Thin superlattices and band-gap discontinuities: The (110) diamond–boron nitride interface

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Abstract
The recent progress in chemical-vapor deposition of diamond on a variety of substrates suggests that diamond may soon be incorporated into electronic devices. As a first step in the investigation of interfaces involving diamond, the linear augmented-plane-wave method is applied to calculate the electronic structure and band-edge discontinuities at the (110) interface of diamond and BN. The use of core levels in identifying the valence-band discontinuity is investigated. By studying N-layer/N-layer C/BN (110) superlattices with N=1, 3, and 5 it is found that three layers of each material are sufficient to give a central layer which has a core-level position nearly representative of the bulk. The calculated valence-band discontinuity is 1.42±0.04 eV, which (using the experimental band gaps of 5.5 eV for diamond and ∼6.2 for BN) leaves a conduction-band discontinuity of 0.7 eV. Due to the heteropolar potential in BN, the lowest conduction band at the interface is the X-point band in BN in spite of the smaller band gap of diamond. This study also shows that the average interstitial potentials in diamond and BN are nearly identical, which suggests another possibility for estimating band discontinuities from bulk quantities alone. The effects of strain at a diamond-on-BN heterojunction are discussed briefly.