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We report on the current density and failure mechanism of bridged Si nanowires epitaxially grown between single crystal Si electrodes. Nanowires were found to handle high threshold current density > 10 5 A/cm 2 before exponentially increasing joule heating increases the resistivity and contributes to a positive feedback loop of thermally induced failure. The physical failure at the center of the bridged nanowires is in agreement with published temperature profile along the nanowire due to Joule heating. It is also an indication of homogeneity and low contact resistance in our bridged nanowire, a desirable property in interfacing nanowires.

The performance of an optical wideband wavelength division multiplexed (WDM) communication system is analyzed considering the effects of stimulated Raman scattering, fiber attenuation and chromatic dispersion. Improved models for the Raman gain and the fiber attenuation constant are proposed, which yield better and reliable performance results of the WDM system. Effect of fiber chromatic dispersion is also investigated and it is observed that dispersion can suitably be selected to overcome the limitations imposed by the stimulated Raman scattering phenomenon.

We fabricated a photo-conducting device with InP nanowires bridged between phosphorous-doped hydrogenated amorphous silicon electrodes. Photoresponse of the device with DC bias was characterized with a white light source and a 630nm He-Ne laser. Experimental results from a large number of devices demonstrate a persistent photoconductivity, a very unique feature of interest. After the light source is shut off, the photogenerated excess carriers recombine very slowly over time and the effect is manifested in the form of persistent photocurrent that takes hours to decay to the dark current level in the range of ~15 nA. Quasi exponential decay of the persistent photocurrent is observed with higher decay rate at the initial stage just after the light source is turned off. Persistent photocurrent magnitude varies with the magnitude of bias voltage, intensity and wavelength of the optical illumination. Experimental decay constant is determined from 0.237/min for -8V bias to 0.174/min for -2V bias. The long recombination time can be attributed to the carrier trapping in the light-induced traps, defects in nanowires and/or in the interface between the nanowires and the amorphous silicon electrodes. Slow recombination process may also originate from the spatial separation of photogenerated electrons and holes by built-in electric fields due to band bending at the heterostructure interfaces between InP nanowire and amorphous silicon electrodes.

We demonstrate an InP nanowire based photodetector laterally integrated between two (111)-oriented vertical silicon surfaces. The nanowires are grown through a simple single step chemical vapor deposition (CVD) process using gold nanoparticles as catalyst with in-situ p-doping and have been heteroepitaxially bridged between a pair of prefabricated pdoped Si electrodes. Nonlinear current-voltage characteristics are observed. Although this nonlinearity resembles a backto-back rectifying profile it originates from space-charge limited conductivity of the nanowires. DC photoelectric characteristics of the device were measured under optical illumination (λ=630 nm) above the bandgap energy (1.34 eV or ~925 nm at room temperature) of InP. The variation in photoconductance with varying input optical power demonstrates high sensitivity of the device to optical illumination.

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Room temperature photoelectrical characterization with 325-nm ultraviolet and 633-nm visible laser excitations is performed on lateral p-type InP nanowires bridged between vertically oriented heavily p-doped single crystal silicon electrodes. Experimental results under 5 V bias demonstrate persistent photoconductivity through a slow decay of excess photocurrent with relaxation times ∼110 s and ∼50 s for the UV and visible laser illuminations, respectively. Persistent photocurrent originates from the long recombination time due to carrier trapping in vacancies, defect centers, and surface states in the InP nanowires. The study opens a new understanding of trap physics of nanowire heterostructures, a critical investigation for applications of these materials in photonic devices.