Semiconductor nanowire based optoelectronic devices: Physics, simulation and design

To address the major challenges in continuing the CMOS technology scaling, a wide variety of technologies are pursued by researchers. One of the promising technologies that are being intensively studied worldwide to develop nanoscale optoelectronic devices is the nanowire based technology. To fully explore the potential of this new technology, theoretical understanding of the behaviors and performances of the nanowire based devices is critically important.;We have pursued model development and computer-aided numerical simulations to investigate the properties of nanowire based p-n homo junctions, nanowire-metal contacts and double heterostructures (DH) for development of optoelectronic devices. Due to the reduced cross-section of the junctions, nanowire based devices exhibit qualitatively different properties from those of bulk cases. These include weaker electrostatic screening and stronger fringing field effects.;First the fringing field effects present in p-n junctions of nanowires and nanowire arrays have been studied. It was found that the depletion width increases as the nanowire radius shrinks. Also the fringing field effects on electrical contact resistivity of semiconductor nanowire-metal contacts have been examined for different contact geometries. It is shown that the contact resistivity increases as the nanowire radius decreases due to fringing field effects. This increase is more significant for nanowire-3D metal contacts than for nanowire-1D metal contacts, and is more significant at low temperatures than at high temperatures. Finally the fringing field effects in nanowire based DH have been analyzed. In general, the junction depletion width in the active region increases for nanowire based DH devices. Such effect becomes more significant as the nanowire radius shrinks. Under the forward bias condition, the overall depletion phenomenon becomes suppressed; therefore the fringing field induced difference also becomes less significant. The results can be used to guide the design and fabrications of nanowire based DH lasers.