Fabrication and characterization of freestanding circular GaN gratings

Abstract

It's of significant interest to combine freestanding nanostructure with active gallium nitride (GaN) material for surface-emitting optoelectronic application. By utilizing bulk micromachining of silicon, we demonstrate here a promising way to fabricate freestanding GaN nanostructures using a GaN-on-silicon system. The well-defined nanoscale circular GaN gratings are realized by fast-atom beam (FAB) etching, and the freestanding GaN gratings are obtained by removing silicon substrate using deep reactive ion etching (DRIE). The freestanding GaN slab is thinned from the backside by FAB etching to reduce the confined modes inside the GaN slab. The measured microphotoluminescence (micro-PL) spectra experimentally demonstrate significant enhancements in peak intensity and integrated intensity by introducing freestanding circular grating. This work represents an important step in combining GaN-based active material with freestanding nanostructures for further increasing light-extraction efficiency.

Optical Forces in Metal/Dielectric/Metal Fishnet Metamaterials in the Visible Wavelength Regime

“…Such freestanding metamaterials can be experimentally realized by using undercutting techniques [40], [41]. They are arranged on a square lattice with 350-nm period.…”

Directive emission of red conjugated polymer embedded within zero index metamaterials

“…The z-axis is normal to the structure surface and the x-y plane is parallel to the structure surface. In order to simplify the design, the structures are considered to be suspended in vacuum; deep etching of a silicon support substrate can be used to achieve this [30][31][32][33]. Au is selected as the metal due to its stability and low ohmic loss.…”

Fabrication and characterization of subwavelength nanostructures on freestanding GaN slab

“…The starting material, consisting of 200nm GaN layer, 450nm AlGaN layer, 200nm AlN buffer layer and 200µm silicon handle layer, is a 20mm×20mm substrate which is cut from a commercial 4-inch GaN template grown on silicon substrate by metal organic chemical vapor deposition (MOCVD). The InGaN/GaN MQWs active layers are deposited on the GaN template by molecular beam epitaxy (MBE) with radio frequency nitrogen plasma as gas source [20][21][22]. A 90nm buffer layer, which incorporated 6nm AlN layer, twelve-period 3nm AlN/3nm GaN superlattice and 12nm GaN layer, was firstly deposited on the GaN template.…”

“…With an etching mask of silica nanospheres, the nanostructure patterns were transferred to the GaN slab by FAB etching [22][23][24], and the residual silica particles were finally removed in buffered HF solution, generating subwavelength nanostructures on the freestanding GaN slab (steps e). Although the freestanding GaN slab has a small downward deflection due to the residual stress [22,24], subwavelength texturing is well conducted in the whole device area. The emission properties of fabricated samples are characterized using a microphotoluminescence (micro-PL) system at room temperature.…”