Despite broad interest in aluminum gallium nitride (AlGaN) optoelectronic devices for deep ultraviolet (DUV) applications, the performance of conventional Al(Ga)N planar devices drastically decays when approaching the AlN end, including low internal quantum efficiencies (IQEs) and high device operation voltages. Here we show that these challenges can be addressed by utilizing nitrogen (N) polar Al(Ga)N nanowires grown directly on Si substrate. By carefully tuning the synthesis conditions, a record IQE of 80% can be realized with N-polar AlN nanowires, which is nearly ten times higher compared to high quality planar AlN. The first 210 nm emitting AlN nanowire light emitting diodes (LEDs) were achieved, with a turn on voltage of about 6 V, which is significantly lower than the commonly observed 20 – 40 V. This can be ascribed to both efficient Mg doping by controlling the nanowire growth rate and N-polarity induced internal electrical field that favors hole injection. In the end, high performance N-polar AlGaN nanowire LEDs with emission wavelengths covering the UV-B/C bands were also demonstrated.

Aluminum nitride nanowire light emitting diodes: Breaking the fundamental bottleneck of deep ultraviolet light sources

AlN nanoneedles with an average tip dimension of ∼15nm were synthesized via a simple vapor deposition method The AlN nanoneedles exhibit excellent field-emission properties with a low turn-on field of 31V∕μm and a high current density of 47mA∕cm2 at the field of 99V∕μm The field enhancement factor for a single nanoneedle is estimated to be as high as 30 000 due to its small tip radius These features make the AlN nanoneedles a competitive candidate for field-emission-based displays

Field emission from AlN nanoneedle arrays

We report a novel approach for growing aligned and orientation-ordered ZnS nanowires. Our method relies on a buffer layer of CdSe grown on a Si(111) substrate, on which ZnS nanowires are grown. The growth process of the nanowire bundles is presented. The technique demonstrated could be an effective pathway for growing patterned, aligned, size-controlled, and orientation-ordered ZnS nanowires.

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Crystal orientation-ordered ZnS nanowire bundles.

The synthesis of novel coaxial C-AlN-C composite nanotubes produced through a chemical substitution reaction in a controllable two-stage process using multiwalled carbon nanotubes (MWCNT) as templates was presented. It was found that the synthesized C-AlN-C composite nanotubes appeared to be slightly faceted. Analysis of the nanotube using EDS revealed the presence of ASl and N within the nanotube with an approximate atomic ratio of 1.00:.97. It was observed that the synthesized nanotubes grown along the [001] direction of the hexagonal AlN, and the (100) plane of AlN is parallel to the (002) plane of graphitic carbon.

Single‐Crystalline AlN Nanotubes with Carbon‐Layer Coatings on the Outer and Inner Surfaces via a Multiwalled‐Carbon‐Nanotube‐Template‐Induced Route

Highly ordered AlN nanowire arrays were synthesized via a simple physical vapor deposition method on sapphire substrate. The nanowires have an extremely sharp tip < 10 nm, with the average length around 3 mu m. Raman spectroscopy analysis on the AlN nanowire arrays revealed that the lifetime of the phonons is shorter than that in bulk AlN. The transmission spectra of the AlN nanowires showed a blueshift similar to 0.27 eV at the absorption edge with that of the bulk AlN, which is closely related to the small size of the nanowires. (c) 2005 American Institute of Physics.

Optical properties of highly ordered AlN nanowire arrays grown on sapphire substrate

AlN nanowires have been successfully prepared via melting Al powder in a NH 3 atmosphere with variable flow rate. The as-prepared nanowires are composed of AlN with diameters of 5 to 40 nm, and lengths of tens of microns. Radian scattering spectra and photoluminescence (PL) of as-prepared AlN nanowires are also investigated. As a result of impurity incorporation and stress, the Raman spectra are shifted to lower frequencies. A blue emission band centered at 434 nm is observed. The PL mechanism of AlN nanowires is discussed.

Chunrong Yin

Papers

Formation and photoluminescence properties of AlN nanowires