GaN-based light-emitting diodes with photonic crystals structures fabricated by porous anodic alumina template

Abstract

In this paper, we propose and demonstrate a convenient and flexible approach for preparation large-area of photonic crystals (PhCs) structures on the GaN-based LED chip. The highly-ordered porous anodic alumina (AAO) with pitch of wavelength scale was adopted as a selective dry etching mask for PhCs-pattern transfer. The PhCs with different pore depths were simultaneously formed on the entire surfaces of GaN-based LED chip including ITO, GaN surrounding contacts and the sidewall of the mesa by one-step reactive ion etching (RIE). The light output power improvement of PhCs-based GaN LED was achieved as high as 94% compared to that of the conventional GaN-based LED.

Gallium Nitride Nanowires and Heterostructures: Toward Color‐Tunable and White‐Light Sources

“…[ 33 ] Fu et al used a highly ordered porous anodic alumina mask to etch photonic crystal structures into the surface of existing thin-fi lm LEDs. [ 34 ] An increase in light output power of 94% with a 20 mA injection current was reported. The extraction effi ciency can also be enhanced through the incorporation of Bragg stacks made of alternating layers of GaN/AlGaN used as a back refl ector in vertical c-axis nanowire arrays.…”

Porous Aluminum Oxide Formed by Anodizing in Various Electrolyte Species

“…Although periodic nanostructures can also be obtained by other nanostructure fabrication techniques represented by photolithography, the ease of anodizing without any expensive equipment is very important for various nanotechnology researchers. Using characteristic nanostructural features, anodic porous aluminum oxide has been widely investigated for many nanoapplications: antireflection structures [134][135][136][137][138][139], reflectors [140][141][142], diodes [143][144][145], plasmonic devices [146][147][148][149], sensors [150][151][152], containers [153,154], catalyst supports [155][156][157], masks [158][159][160], emulsification filters [161,162], magnetic recording media [163][164][165], memory devices [166][167][168], photovoltaic devices [169], nanomeshes [170], etc. Greatly wide-ranging applications of anodic porous oxides have been reported to date.…”

Optical Properties of Nanoporous Anodic Alumina and Derived Applications

“…These applications can be even improved when the p-AAO is used as a template to pattern other materials such as ordered polymer nanopillar arrays [77,78]. This nanopatterning technique has been demonstrated useful for improving the light extraction in GaN-based LEDs where the highly ordered p-AAO was used as a selective dry etching mask on the entire surfaces of the devices, achieving a light output improvement of as much as 94 % [79][80][81]. The photonic crystal properties of p-AAO have even been used to investigate the optical properties and composition of the material itself, as in the work of Choi et al [25], where the combination of modeling and measurement of transmittance through the 2-D nanostructure of perfect p-AAO-based photonic crystals makes possible to demonstrate that the oxide layers at the pore walls are actually composed of two layers: the outermost with the highest concentration of incorporated electrolyte anions and innermost with a more pure barrier-like aluminum oxide.…”

“…This happens because of two main factors: (i) its porous structure is adequate for integrating the necessary fluidic circuits with the optical setup and (ii) its great surface-to-volume ratio permits a great amplification factor of the changes in the surface, even for small amounts of the species to be detected. Nevertheless, optical properties of p-AAO are also the basis of other applications not directly related to sensing, as for instance the extraction of light from LEDs [79,96] (where the p-AAO nanostructure serves as a texturizing template for the LED surface), the generation of laser emission [76] (where the self-arrangement of pores contributes to create cavity modes to amplify laser light emitted by a gain material infiltrated within the pores), to texturize surfaces and interfaces of photovoltaic cells to improve light absorption or charge collection in the energy conversion process [97], or even to create unique photonic barcodes for labeling applications [98]. Doing an extensive review of all the applications based on the optical properties would require a much longer extent than this chapter.…”

“…for fabricating an improved light transmission surface [79]. In this work, a complex geometry of the p-AAO pores where the pore diameter decreases with depth is fabricated.…”