Numerical analysis of electronic state of CNT/BNNT heterojunction

Abstract

The I-V characteristics of CNT/BNNT heterojunctions, which comprise quantum double barrier systems (DBS), were numerically investigated using density functional theory (DFT) calculations and the non-equilibrium Green’s function (NEGF) method. First, we performed a structural optimisation of the DBS of CNT/BNNT. Next, the I-V characteristics of the heterojunctions were calculated using the SIESTA package. The I-V characteristics remain flat up to a certain bias voltage, and then the current increases with increasing voltage. Our CNT/BNNT double-barrier heterojunctions have resonant states inside the barriers as semiconductor-based double-barrier diodes; these states determine the transmission function. An energy gap was centred at the Fermi energy and sharp peaks in the gap were observed. It was also found that the energy interval of the peaks near the Fermi energy was dependent on the separation length of the two BNNT barriers. Using projected density of states (PDOS) analysis, we also investigated the local behaviour of electrons in the devices.