Optical Properties of Monodispersed AlGaN Nanowires in the Single-Prong Growth Mechanism

Abstract

Growth of mono-dispersed AlGaN nanowires of ternary wurtzite phase is reported using chemical vapour deposition technique in the vapour-liquid-solid process. The role of distribution of Au catalyst nanoparticles on the size and the shape of AlGaN nanowires are discussed. These variations in the morphology of the nanowires are understood invoking Ostwald ripening of Au catalyst nanoparticles at high temperature followed by the effect of single and multi-prong growth mechanism. Energy-filtered transmission electron microscopy is used as an evidence for the presence of Al in the as-prepared samples. A significant blue shift of the band gap, in the absence of quantum confinement effect in the nanowires with diameter ~ 100 nm, is used as a supportive evidence for the AlGaN alloy formation. Polarized resonance Raman spectroscopy with strong electron-phonon coupling along with optical confinement due to the dielectric

Molecular beam epitaxy growth of Al-rich AlGaN nanowires for deep ultraviolet optoelectronics

“…[5][6][7][8] As an alternative path to achieve high efficiency UV LEDs and lasers, AlGaN nanowire structures have drawn considerable attention. [18][19][20][21][22][23][24][25][26][27][28][29][30] The promise of AlGaN nanowires stems not only from their low defect densities, but more importantly, their surface enhanced p-type dopant (Mg) incorporation. It has been demonstrated, both experimentally and theoretically, that Mg-dopant incorporation is significantly enhanced in AlN, InN, and GaN nanowire structures compared to their bulk counterparts, 26,[31][32][33] thereby promising very efficient p-type conduction in wide bandgap Al-rich AlGaN that was not possible previously.…”

“…However, with the use of conventional chemical vapor deposition processes, Al-rich AlGaN nanowire structures only yield defect-related emissions in the wavelength range >300 nm. [18][19][20][21][22] Recent studies have shown that spontaneously formed AlGaN nanowire heterostructures with significantly improved optical and electrical properties can be realized via catalyst-free molecular beam epitaxy (MBE). [23][24][25][26][27][28][29][30][34][35][36][37][38] wavelengths of LEDs and lasers using such spontaneously formed AlGaN nanowires have been limited to 250 nm, or longer.…”

Polarized Raman and photoluminescence studies of a sub-micron sized hexagonal AlGaN crystallite for structural and optical properties

“…S2, is assigned as AlN‐ mode. The observation of GaN‐ mode along with the AlN‐ in a single Raman spectrum recorded from a single hexagonal sub‐microcrystal indicates the two‐mode behavior of the phonons in the random alloy formation of the AlGaN phase . We observed the similar spectra obtained from a single spot on the tip of the crystals also (not shown figure).…”

“…The peak centered at 3.47 eV is assigned to the free exciton (FE) recombination of electron–hole pair from conduction band edge to the valence band edge of GaN (with nominal Al percentage in our study). The luminescence peak observed at 3.32 eV is originated because of the recombination of the neutral donor–acceptor pair (DAP; D 0 A 0 ), because of a transition from a shallow donor state of nitrogen vacancy (V N ) to a deep acceptor state of V Ga . The variation in intensity for different polarization configurations or polarization anisotropy is dependent on the material geometry as well as the anisotropic properties of crystalline medium.…”

The light–matter interaction of a single semiconducting AlGaN nanowire and noble metal Au nanoparticles in the sub-diffraction limit

“…The PL emission at 3.53 eV is reported to originate because of the recombination of free exciton (FE) from the conduction band minimum to the valence band maximum, [25] as shown in the schematic band-diagram ( Figure 6(b)). The emission peak observed at 3.30 eV is because of the recombination of the neutral donor-acceptor pair (DAP; D 0 A 0 ), with nitrogen vacancy (V N ) as the shallow donor and Ga vacancy (V Ga ) as a deep acceptor state [25].…”