Fabrication of InGaN/GaN nanorod light-emitting diodes with self-assembled Ni metal islands

Abstract

We report the fabrication of InGaN/GaN nanorod light-emitting diodes (LEDs) using inductively coupled plasma reactive-ion etching (ICP-RIE) and a photo-enhanced chemical (PEC) wet oxidation process via self-assembled Ni nanomasks. An enhancement by a factor of six times in photoluminescence (PL) intensities of nanorods made with the PEC process was achieved in comparison to that of the as-grown structure. The peak wavelength observed from PL measurement showed a blue shift of 3.8 nm for the nanorods made without the PEC oxidation process and 8.6 nm for the nanorods made with the PEC oxidation process from that of the as-grown LED sample. In addition, we have demonstrated electrically pumped nanorod LEDs with the electroluminescence spectrum showing more efficiency and a 10.5 nm blue-shifted peak with respect to the as-grown LED sample.

Influence of stress on optical transitions in GaN nanorods containing a single InGaN/GaN quantum disk

“…Only five measurement points were considered in the thinner nanorods: points 1 and 5 correspond to the two edges of the SQD, point 3 lies at its center, and point 2 (4) lies approximately mid-way between points 1 (5) and 3. Since the width of the relaxed outer shell will be independent of nanorod diameter, 7 the impact of reducing the nanorod diameter will be to increase the contribution of the outer shell contributes to the volume excited by the electron beam relative to that contributed by the strained inner core. Thus, the lower energy CL peak (2.78 eV) will be more dominant in the spectrum than the emission at 2.84 eV from the strained nano-disk core, as observed in Fig.…”

“…[2][3][4][5][6][7][8][9][10] Compared with other III-V semiconductors, the III-nitrides show strong polarization especially along the c-axis with the effect that strain can have a major influence on the optical properties in In x Al y Ga 1-x-y N based quantum wells (QWs). 11 The formation of a nanorod structure, either by bottom-up epitaxial growth [2][3][4][5] or by dry etching a pre-existing epitaxial III-nitride layer, [6][7][8][9][10] has been proposed as a mean of alleviating strain due to the free surface presented by the sidewalls enabling the lattice to relax. [12][13][14] In the case of homogeneous nanorods formed by dry etching from c-plane homo-epitaxial GaN templates, the degree of strain relaxation in the overall structure will depend on the diameter and height of the nanorods, with complete strain relaxation occurring when their height exceeds their diameter irrespective of the type of substrate used.…”

GaN based nanorods for solid state lighting

“…The GaN nanorods were defined by various methods like conventional photolithography, e-beam lithography, and nanoimprint lithography, or other low cost methods, for example, nanoscale self-organized nickel islands as etching mask or SiO 2 nanosphere lithography. [115][116][117][118] Dry etching methods, such as RIE-ICP, were used to achieve high aspect ratio GaN nanopillars.…”

“…115,116,118,120 However, using a top-down method, a large portion of GaN material is etched away and does not contribute to light emission any more. This will add additional cost during device fabrication compared to the bottom-up (growth) method.…”

Highly Efficient and Bright LEDs Overgrown on GaN Nanopillar Substrates

“…During the NELOG process, coalescence overgrowth of nanostructures not only improves crystal quality [18], but also produces a scattering effect on the emitted photons, leading to higher light-extraction efficiency (LEE) [19]. The nanostructures were generally fabricated by top-down methods [20]- [22], such as etching process, in which the dry etching procedure normally generates defect states on the column surfaces, causing reduction of internal quantum efficiency (IQE). In this paper, we report a NELOG of high-quality GaN layer on bottom-up nanostructure [self-assembled GaN nanopillars (NPs)] grown by molecular beam epitaxy (MBE) [23].…”