0000000000628003
AUTHOR
Li-chyong Chen
UV light induced luminescence processes in AlN nanotips and ceramics
UV induced luminescence properties of AlN (Eg = 6.2 eV) have been studied for AlN nanotips and AlN ceramics, using methods of photoluminescence, optically stimulated luminescence and thermoluminescence. In both types of objects the main luminescence band, which appears in prompt and stimulated emission spectra around 400 nm, arises due to presence of oxygen-related defects. The main difference between AlN nanotips and AlN ceramics is observed in excitation spectra and TL properties. Basing on the experimental results it is assumed that several different energy transfer mechanisms occur in AlN. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Spectral characterization of bulk and nanostructured aluminum nitride
Spectral characteristics including photoluminescence (PL) spectra and its excitation spectra for different AlN materials (AlN ceramics, macro size powder and nanostructured forms such as nanopowder, nanorods and nanotips) were investigated at room temperature. Besides the well known UV-blue (around 400 nm) and red (600 nm) luminescence, the 480 nm band was also observed as an asymmetric long-wavelength shoulder of the UV-blue PL band. This band can be related to the luminescence of some kind of surface defects, probably also including the oxygen-related defects. The mechanisms of recombination luminescence and excitation of the UV-blue luminescence caused by the oxygen-related defects were …
Carrier dynamics in epilayers and nanocolumns of ternary AlGaN with a tunable bandgap
We apply several optical time-resolved techniques to investigate the dynamics of excess carriers in AlxGa1−xN nanocolumns grown on (111) silicon substrates and in thick AlxGa1−xN epitaxial layers deposited on sapphire. We demonstrate that carrier lifetime drops in nanocolumns by several times if compared to epilayers with similar Al content; in addition, recombination rate displays a strong nonlinearity on excitation. On the other hand, carrier localization effects observed in the epilayers completely disappear in nanocolumns.
Luminescence properties of wurtzite AlN nanotips
The optical properties of aluminum nitride nanotips (AlNNTs) synthesized via vapor transport and condensation process have been studied by cathodoluminescence, photoluminescence (PL), thermoluminescence (TL), and UV absorption measurements. Two defect related transitions around 2.1 and 3.4eV and an excitonic feature at 6.2eV were identified. Compared to the AlN macropowders, the AlNNTs showed a blueshift (+0.2eV) of the ∼3.2eV peak. Analysis of both PL and TL excitation measurements indicated the existence of subband gap multiple energy levels in AlNNTs. A significant TL intensity even at 145°C suggests possible ultraviolet detector and dosimetric applications of these AlNNTs.