We design two p-n nanojunctions based on S- and Si- atoms doped armchair blue phosphorene nanoribbons (aBPNRs) including two semi-infinite electrodes and a scattering region and investigate their electronic and transport properties. Our calculations are based on density functional theory incorporated non-equilibrium Green's function approach. In impure aBPNRs, S/Si atoms substituted doping could greatly enhance the conductivity, and the S/Si doped aBPNRs show metallic properties. Based on the doped aBPNRs, devies D1 and D2 are constructed where the scattering region of D1 is formed by direct expansion of two electrodes, while the scattering region of D2 includes two undoped unit cells as buffer. The transport calculations show that both of D1 and D2 show excellent negative differential resistance (NDR) effect at low bias and significant rectification effects at high bias. Moreover, whether there is buffer in the scattering region has a great influence on the magnitude of current of the devices. Although the current of the device D1 without buffer is generally higher than that of the device D2, the NDR and rectification effects of D2 are better than D1 in terms of peak-to-valley ratio and rectification rate. These transport behaviors can be explained by the evolution of the transmission spectra, frontier molecular orbital and the symmetry matching between the band structures of the electrodes. This indicates that aBPNRs are a promising candidate for the future application of multi-functional electronic devices.
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