| AVS 55th International Symposium & Exhibition | |
| Nanometer-scale Science and Technology | Tuesday Sessions |
| Session NS+NC-TuA |
| Session: | Nanowires and Nanosize Effects |
| Presenter: | J.P. Long, Naval Research Laboratory |
| Authors: | J.P. Long, Naval Research Laboratory A.J. Makinen, Naval Research Laboratory B.S. Simpkins, Naval Research Laboratory M.A. Mastro, Naval Research Laboratory P.E. Pehrsson, Naval Research Laboratory |
| Correspondent: | Click to Email |
Photoluminescence (PL) from single semiconducting nanowires (NWs) can exhibit considerable variability along a NW length and among NWs from the same growth batch. While the cause of the variability remains a subject of research and may be related to structural or chemical heterogeneities, here we report a purely optical source of variability caused by microcavity effects within the NW. Such effects must be considered whenever the transverse dimension of a transparent nanostructure exceeds ~λ/2n, where λ is the free-space wavelength and n is the index of refraction. In our experiments, spatially and spectrally resolved micro-PL excited with 325-nm radiation was recorded at room temperature in a ~20-micron long GaN NW with a triangular cross section. An important feature of the NW was a gradual taper in width, from about 1 micron to less than tens of nanometers, that permitted recording the optical response as the NW width varied. The NW emitted band-gap radiation near 375 nm and a broad defect band beginning at ~475 nm and extending to longer wavelengths. The spectrally resolved PL exhibits periodic intensity modulations along the NW length. The periodicity is consistent with enhanced emission occurring when the PL wavelength satisfies the requirement for a transverse standing wave within the NW. We attribute the PL modulation to either or both of two mechanisms, namely a microcavity modulation of emission probability (the “Purcell effect”) or a Fabry-Perot etalon effect that modulates the external radiation of internally generated PL.