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Impurity-derived <i>p</i> -type conductivity in cubic boron arsenide
摘要： Cubic boron arsenide (c-BAs) exhibits an ultrahigh thermal conductivity (j) approaching 1300 Wm(cid:2)1 K(cid:2)1 at room temperature. However, c-BAs is believed to incorporate high concentrations of crystal imperfections that can both quench j and act as sources of unintentional p-type conductivity. Although this behavior has been attributed to native defects, we show here, using optical and magnetic resonance spectroscopies together with first-principles calculations, that unintentional acceptor impurities such as silicon and/or carbon are more likely candidates for causing the observed conductivity. These results also clarify that the true low-temperature bandgap of c-BAs is 0.3 eV higher than the widely reported value of (cid:3)1.5 eV. Low-temperature photoluminescence measurements of c-BAs crystals reveal impurity-related recombination processes (including donor-acceptor pair recombination), and electron paramagnetic resonance experiments show evidence for effective mass-like shallow acceptors. Our hybrid density functional calculations indicate that native defects are incapable of giving rise to such signals. Instead, we find that group-IV impurities readily incorporate on the As site and act as shallow acceptors. Such impurities can dominate the electrical properties of c-BAs, and their influence on phonon scattering must be considered when optimizing thermal conductivity.
关键词： thermal conductivity,first-principles calculations,p-type conductivity,photoluminescence,impurities,cubic boron arsenide,electron paramagnetic resonance
更新于2025-09-04 15:30:14
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Tunnel spectroscopy of localised electronic states in hexagonal boron nitride
摘要： Hexagonal boron nitride is a large band gap layered crystal, frequently incorporated in van der Waals heterostructures as an insulating or tunnel barrier. Localised states with energies within its band gap can emit visible light, relevant to applications in nanophotonics and quantum information processing. However, they also give rise to conducting channels, which can induce electrical breakdown when a large voltage is applied. Here we use gated tunnel transistors to study resonant electron tunnelling through the localised states in few atomic-layer boron nitride barriers sandwiched between two monolayer graphene electrodes. The measurements are used to determine the energy, linewidth, tunnelling transmission probability, and depth within the barrier of more than 50 distinct localised states. A three-step process of electron percolation through two spatially separated localised states is also investigated.
关键词： quantum information processing,hexagonal boron nitride,tunnel spectroscopy,localised electronic states,graphene
更新于2025-09-04 15:30:14