Growth and Optical Properties of Highly Uniform and Periodic InGaN Nanostructures

Abstract

Low-dimensional semiconductor structures, such as quantum dots (QDs), give rise to new physical phenomena that have been applied in optoelectronic and electronic devices, for example, QD laser diodes [1] and single-electron transistors. [2] To date, the formation of semiconductor dots on the nanometerscale is mostly controlled by the Stranski-Krastanow (S-K) growth mode, [3] where the self-organized formation of nanoislands is driven by the strain energy in large-lattice-mismatch systems. An alternative technique to form semiconductor QDs is by droplet expitaxy, which relies on the self-assembly of liquid metal nanoparticles of group III atoms and their crystallization into III-V semiconductor QDs by a subsequent supply of group V atoms. [4][5][6] In the self-organized processes described above, random distribution of the QD sizes and locations usually occurs, [7] which limits the benefits from low-dimensional structures. Usually, the dynamics of exciton decay are found to be monoexponential and the emission from a single dot should be very narrow. However, the disorder of the QD system governs the recombination dynamics to give a nonexponential photoluminescence (PL) decay of the entire QD ensemble.[8] Furthermore, the disorder also produces many problems in continuous wave (cw) PL experiments, in which the width of the emission spectra reflects the inhomogeneous broadening owing to the dispersion of both dot sizes and locations. One should be extremely careful when using the cw PL technique to measure unambiguously the energy and the linewidth of light emission from the QD system. [9] To obtain nanodots with homogeneous size and controlled positioning, various methods have been carried out to promote nucleation at expected sites. These methods can be divided into two categories in principle. The first is by surfacestate control, [10][11][12] such as by self-organized anisotropic strain engineering, [10] by using vertical elastic interaction in QD superlattices, [11] by ion sputtering-induced surface instability, [12] and so forth. Locally ordered nanodot arrays were produced by these methods. The other sort of approach relies on nanoscale selective area epitaxy (NSAE) on a prepatterned substrate or growth template. The nanopatterning of substrates/templates can be realized by a variety of lithographic or nonlithographic techniques, such as interference lithography, [13,14] anodic oxidation of aluminum to form nanoporous alumina, [15][16][17][18] nanosphere lithography, [19] focused ion beam sputtering, [20] and electron-beam lithography (EBL). [21][22][23][24] At present, state-of-the-art EBL allows the creation of patterns with versatile physical geometry and localization, and homogeneous, tunable size. Rigorously aligned InAs/GaAs nanodot arrays with a standard deviation of less than 5 % for both dot diameter and height were achieved by molecular beam epitaxy (MBE) on an EBL-patterned GaAs substrate.[23] Well-resolved excited states of the homogeneous QDs were observed by power-dependent PL measurements. [24]...

Single photon emission from site-controlled InGaN/GaN quantum dots

“…[11] To control the position of a III-N QD, various approaches have been explored. [12][13][14][15][16][17][18] To date, QD-like emission has only been reported from dots formed at the apex of a sitecontrolled GaN pyramid [12,17] and dots at the top of a site-controlled AlGaN nanowire. [18] But no single photon emission has been reported from these systems yet.…”

Origin of broad luminescence from site‐controlled InGaN nanodots fabricated by selective‐area epitaxy

“…2). Nanoring structures are observed in this stage [16][17][18]. As growth proceeded, the effect of growth rate anisotropy started to coalesce different crystal planes around the edge toward the center of the nanoring (Stage II, Fig.…”

Template-directed selective growth of ordered ZnO nanostructures on GaN by the hydrothermal method

“…At the low growth temperature of 90 1C, probably only the nuclei formed at the nanohole edges can grow into crystallites, leading to the formation of doughnut-like nanostructures. This kind of doughnut-like nanostructures were also observed in the selective growth of III-nitride materials by MOCVD [18,19]. The positional variation of nucleation probability in nanometer scale can also lead to the growth of ZnO nanotubes with single or multiple channels [20].…”