Creation of regular arrays of faceted AlN nanostructures via a combined top-down, bottom-up approach

Abstract

The realisation of spatially-determined, uniform arrays of faceted aluminium nitride (AlN) nanostructures has had limited exploration, largely due to the fact that selective area growth of AlN via MOVPE (Metal Organic Vapour Phase Epitaxy) has not been realised. Instead, this paper reports the use of a combined top-down, bottom-up approach to realise well-faceted, highly-uniform, periodic nanotextured AlN surfaces. MOVPE regrowth is performed upon dry-etched AlN nanorods and nanoholes, and we present a study into the effect of the growth conditions on the resulting faceting and morphology. Specifically, growth temperature, V/III ratio and growth time are investigated and analysed via scanning-electron and atomic-force microscopy. The V/III ratio was found to influence the nanostructure morphology most whilst the growth temperature was found to have much less of an impact within the temperature range studied. Experiments with a longer growth time are performed to create nanostructures for potential use in applications, such as for AlGaN-based quantum-well or quantum-dot emitters.

Organized AlN Nanowire Arrays by Hybrid Approach of Top-Down Processing and MOVPE Overgrowth for Deep UV Emission Devices

“…The first one is chosen to be similar to the usual growth conditions of planar c -oriented AlN: , growth under a H 2 atmosphere at 1200 °C and 100 mbar using TMAl and NH 3 precursors with respective fluxes of 7.36 and 2230 μmol min –1 , corresponding to a low V/III ratio equal to 300 (sample called “low V/III”). The second one is the same except for the NH 3 flux, which is now 201 000 μmol min –1 leading to a significant V/III ratio equal to 27 000 (sample called “high V/III”), in accordance with the already reported AlN overgrowth on wire geometry. , The growth time is 1 h 30 min for both samples, corresponding to the deposition of approximately 225 nm AlN for the high V/III recipe and 190 nm AlN for the low V/III one (for the S = 5 μm and D initial = 500 nm pillars). SEM observations of the samples after the MOVPE regrowth for both recipes and for the three diameters ( S = 5 μm; D initial = 2 μm, 500 nm, and 250 nm) are shown in Figure a–f.…”

“…The second one is the same except for the NH 3 flux, which is now 201 000 μmol min −1 leading to a significant V/III ratio equal to 27 000 (sample called "high V/III"), in accordance with the already reported AlN overgrowth on wire geometry. 26,54 The growth time is Anisotropic growth features, with elongated stripes along a⃗ , are clearly distinguishable on the m-surface sidewalls of the AlN nanowires using the low V/III recipe. These features can be interpreted as a specific diffusion process existing for the Al adatoms on the m-surfaces.…”

UV emission from MOVPE nanowire LEDs

“…UV-C emission has been achieved with core-shell AlGaN/AlN quantum wells (QWs) with demonstration of emission until 230 nm. 3 Nevertheless, the fabrication of UV-LED based on the AlN approach is impeded by the p-doping issue of AlN. On the contrary, the "GaN nanowires" approach is suitable to make UV-LED that allows the efficient electrical injection through the n-doping of GaN nanowire.…”

Articulation of synthesis methods and approach for nanosized materials: a literature review

“…Además, los enfoques top-down y bottom-up son utilizados como enfoque y estrategia de síntesis destructiva en forma descendente a partir de la fragmentación de macropartículas y constructiva en forma ascendente desde átomos o moléculas, respectivamente, para obtener diferentes sistemas de MNs metálicos y no metálicos, etc. [4][5][6][7][8][9][10][11][12][13]. Desde otra perspectiva, la formación de MNs se puede obtener de acuerdo con la naturaleza del medio que impone el método en que se someten las partículas.…”