Electrical field induced direct-to-indirect bandgap transition in ZnO nanowires

As a wide bandgap (3.37 eV) compound semiconductor with the exciton binding energy of 60 meV, ZnO nanowires have attracted considerable interest because of great potential applications in micro-optoelectronics and nano-optoelectronics. However, ZnO nanowires as basic units of microelectronic and optoelectronic nanodevices usually work in the circumstance of the electrical field. Therefore, the influence of electrical field on the electronic structure of ZnO nanowires partly determines the performance of nanodevices. For this issue, we inhere have studied the effects of the applied electrical field on the electronic structure of ZnO nanowires using the density functional theory. It was found that the applied electrical field cannot only effectively modulate the bandgap of ZnO nanowires but also leads to the bandgap transition from direct to indirect. Meanwhile, the above effects of electrical field depend on the size and shape of ZnO nanowires. The physical understanding of the electrical field effects of the energy band structure of ZnO nanowires is attributed to the bond length changes in lattice and the charge transfer between Zn and O atoms. Thus, these valuable investigations are important for designing the microelectronic and optoelectronic nanodevices based on ZnO nanowires. (C) 2010 American Institute of Physics. [doi:10.1063/1.3462407]