Influence of Surface passivation on Band alignment and Exciton binding energy in monolayer-BN/Diamond Heterostructures

There is a growing interest in ultra-wide bandgap materials for the development of UV-visible optoelectronics. As a material system for next-generation devices, we investigate the heterojunction formed between hexagonal boron nitride (hBN) and Diamond-111. Both materials have shown exciton binding energy greater than room temperature (25 meV), low lattice mismatch ~0.72%, and wafer size scalability, enabling the fabrication of wafer-sized heterostructures with excitons stable at room temperature. In this work, we present how the bandgap, conduction, and valence bands characteristics of monolayer-hBN/Diamond-111 heterostructures change with respect to Diamond passivation, thickness, and high symmetry interface stacking within DFT calculations using Quantum Espresso. For optical properties, we performed quasiparticle correction and calculated exciton binding energies within BerkeleyGW for heterostructures with different passivation. Our findings show a tunable indirect bandgap in real and k-space with large exciton binding energies.