Due to the high surface to volume ratio, nanowire based components benefit from new properties typical of the nanoscale. ZnO nanowires have already proved their usefulness in the realization of multiple electronic components, such as FET transistors, gas detectors, photodetectors, LEDs or even solar cells.
ZnO nanowires have also shown themselves to be very promising UV detectors thanks to their significant photoconductive gain, as high as G =10^8 . This makes them suitable for single photon detection, or at least detection of very dim light. The main current drawback is the recovery time (minimum time between 2 detections) which we develop last hours.
The device we developed is a good candidate for opto-electronic applications. Our device is a photodetector with ohmic contact and it behaves like a transistor. Our experiments stress out the importance of surface effect on the electrical by taking measurements in different atmospheres (oxygen, air, vacuum and argon). These surface states are the reason for the existence of a photoconductive gain, we obtain a maximum gain of G =6.10^6. In counterpart of this great gain, the persistence of the photocurrent (which can last up to several hours) prevents the device from operating at high frequency. We propose a method to reduce this time by applying a gate voltage.
 C. Soci , A. Zhang, B. Xiang, S. A. Dayeh, D. P. R. Aplin, J. Park, X. Y. Bao, Y. H. Lo, and D. Wang, Nano Lett. 7, 1003 (2007).
Time integrated and time resolved microphotoluminescence studies have been performed on InxGa1-xN quantum
disks embedded in GaN nanocolumns. The results are analysed in context of current theories regarding an
inhomogeneous strain distribution in the disk, which is theorised to generate lateral charge separation in the
disks by strain induced band bending, an inhomogeneous polarization field distribution, and Fermi surface
pinning. It is concluded that no lateral separation of carriers occurs in the quantum discs under investigation.
We present an investigation of free-carrier screening in coupled asymmetric GaN quantum discs with embedded AlGaN barriers using time-integrated and time-resolved micro-photoluminescence measurements, supported by three-dimensional multi-band k.p computational modeling. We observe that with increasing optical excitation the carrier lifetime decreases and emission energy blue-shifts. This originates from the screening of built-in piezo- and pyroelectric fields in the quantum discs by photo-generated free-carriers. Due to non-resonant tunneling of carriers from the smaller disc to the larger disc, free carrier screening is enhanced in the larger disc. The non-resonant tunneling was found to have a significant role in samples with a thin barrier, as the screening decreased with barrier thickness (i.e. decreased tunneling). Computational modeling was in good agreement with the experimental results.
We present measurements of microphotoluminescence decay dynamics for single InGaN quantum dots. The recombination is shown to be characterized by a single exponential decay, in contrast to the non-exponential recombination dynamics seen in the two-dimensional wetting layer. The lifetimes of single dots in the temperature range 4 K to 60 K decrease with increasing temperature. Microphotoluminescence measurements of exciton complexes in single MOVPE-grown InGaN quantum dots are also reported. We find the exciton-biexciton and exciton-charged exciton splitting energies to be 25 meV and 10 meV to the higher-energy side of the exciton ground state, respectively. Assignments of the ground state exciton, biexciton and charged exciton are supported by theoretical calculations. These measurements have been extended to investigate the time-resolved dynamics of biexciton transitions in the quantum dots. The measurements yield a radiative recombination lifetime of 1.0 ns for the exciton and 1.4 ns for the biexciton. The data can be fitted to a coupled differential equation rate equation model, confirming that the exciton state is refilled as biexcitons undergo radiative decay.