Optical performance of top-down fabricated InGaN/GaN nanorod light emitting diode arrays

Abstract

Vertically aligned InGaN/GaN nanorod light emitting diode (LED) arrays were created from planar LED structures using a new top-down fabrication technique consisting of a plasma etch followed by an anisotropic wet etch. The wet etch results in straight, smooth, well-faceted nanorods with controllable diameters and removes the plasma etch damage. 94% of the nanorod LEDs are dislocation-free and a reduced quantum confined Stark effect is observed due to reduced piezoelectric fields. Despite these advantages, the IQE of the nanorod LEDs measured by photoluminescence is comparable to the planar LED, perhaps due to inefficient thermal transport and enhanced nonradiative surface recombination.

III-nitride core–shell nanowire arrayed solar cells

“…This forms the semi-periodic array of vertically-aligned nanowires that are tapered with wider diameters at the base, have an average pitch of ~500 nm determined by the diameter of the colloidal silica spheres, and are uniform in height (~900 nm). The sample is then etched in an anisotropic KOH-based (AZ400K photoresist developer) wet etch that removes surface damage from the ICP etch [20] and forms ~100 nm diameter cylindrically shaped nanowires. A nanowire template made this way, but using a colloidal silica sphere diameter of ~1 m, is shown in the scanning electron microscope (SEM) image in Fig 2(a).…”

“…Planes perpendicular to the Ga polar (0001) top facet etch faster resulting in micro-faceted sidewalls with preferred m-plane exposed facets and a (0001) c-plane top facet. This fabrication technique [20] has several advantages including all the nanowires of the same height, the sidewalls have defined crystal facets, and dry etch damage is removed.…”

“…The core GaN nanowires are created by a "top-down" fabrication scheme. It uses a colloidal silica mask [20] and wet and dry etching steps to create a semi-periodic array with an average pitch of ~500 nm (left grouping in Fig. 1(a)) and ~900 nm height.…”

“…1(a)) and ~900 nm height. The cylindrically shaped nanowires have straight micro-faceted sidewalls with preferred [20] m-plane exposed facets, and a top (0001) c-plane facet. Next radial growth of the InGaN/GaN MQW absorbing shell layers (middle grouping of nanowires in Fig.…”

Efficiency enhancement of InGaN amber MQWs using nanopillar structures

“…It is known that the surface damage as a non-radiative recombination channel was usually introduced during the dry etching process and the density of surface damage depends on the total surface area of the nanopillar sidewall [26]. The structure density of the nanopillar and the sidewall surface area (which is normalized to the one of the NP900 nm sample) have been calculated for all the samples and are listed in Table 2.…”