Layer number dependent optical properties of multilayer hexagonal BN epilayers

作者：Du X Z; Uddin M R; Li J; Lin J Y; Jiang H X^*

来源：Applied Physics Letters, 2017, 110(9): 092102.

DOI：10.1063/1.4977425

Deep ultraviolet photoluminescence emission spectroscopy has been employed to probe the layer number dependent near band-edge transitions above 5 eV in multilayer hexagonal boron nitride (h-BN) epilayers grown by metal-organic chemical vapor deposition. Two emission lines near 5.30 and 5.47 eV were resolved at 10 K. These two emission lines share similar spectroscopic features, and their energy peak separation is nearly independent of the number of layers. The observed energy separation of similar to 172 meV coincides well with the in-plane phonon vibration mode, E-2g, having an energy of 1370 cm(-1) (similar to 172 meV). The results suggested that the emission line at similar to 5.30 eV and similar to 5.47 eV are a donor-acceptor-pair transition and its one E-2g phonon replica, respectively. When the number of layers decreases from 100 to 8, the emission peak positions (E-p) of both emission lines blueshifted monotonically, indicating the dimensionality effects on the optical properties of h-BN. The layer number dependence of E-p can be described by an empirical formula, which accounts for the variations of the energy bandgap and activation energies of impurities with the number of layers. The results revealed that the impurity activation energies and the carrier-phonon coupling strength increase as the dimensionality of h-BN scales from thick layer to monolayer, suggesting that it is more difficult to achieve conductivity control through doping in monolayer or few-layer h-BN than in thick h-BN. Published by AIP Publishing.

• 出版日期2017-2-27