An epitaxial layer of an InGaN light-emitting diode (LED) structure was separated from a truncated-triangle-striped patterned-sapphire substrate through a chemical lift-off (CLO) process. A crystallographic stable and terminated V-shaped GaN grooved pattern was observed on the lift-off GaN surface. A peak wavelength blueshift phenomenon of the micro-photoluminescence spectrum was observed on the lift-off LED epitaxial layer (440.7 nm) compared with the LED/sapphire structure (445.8 nm). The free-standing LED epitaxial layer with a 453 nm electroluminescence emission spectrum was realized through a CLO process with the potential to replace the traditional laser lift-off process for vertical LED applications. (c) 2010 The Japan Society of Applied Physic
InGaN light-emitting diodes (LED) were grown on a truncated-triangle-striped patterned sapphire substrate. After growing a GaN layer on the patterned-sapphire substrate, it was observed that a higher lateral growth process formed a V-shaped-striped air-void structure. After a bottom-up N-face wet etching process on a GaN layer, the stable crystallographic etching planes were formed as the GaN{10 (1) over bar(1) over bar} planes. Treated LED structures had 65% light enhancements and smaller divergent angles. A rhombus-like air-void structure formed at GaN/patterned-sapphire interface provided a high light extraction process and a wet etching channel for a chemical lift-off process application. (C) 2010 The Japan Society of Applied Physic
The conical air-void structure of an InGaN light-emitting diode (LEDs) was formed at the GaN/sapphire interface to increase the light extraction efficiency. The fabrication process of the conical air-void structure consisted of a dry process and a crystallographic wet etching process on an undoped GaN layer, followed by a re-growth process for the InGaN LED structure. A higher light output power (1.54 times) and a small divergent angle (120°) were observed, at a 20 mA operation current, on the treated LED structure when compared to a standard LED without the conical air-void structure. In this electroluminescence spectrum, the emission intensity and the peak wavelength varied periodically by corresponding to the conical air-void patterns that were measured through a 100 nm-optical-aperture fiber probe. The conical air-void structure reduced the compressed strain at the GaN/sapphire interface by inducing the wavelength blueshift phenomenon and the higher internal quantum efficiency of the photoluminescence spectra for the treated LED structure.
The truncated-conical air-hole (TAH) array structure of an InGaN light-emitting diode (LED) was fabricated on the mesa-edge region to increase the light extraction efficiency. The fabrication consisted of a dry process and a crystallographic wet etching process on the AlN buffer layer to form a truncated-conical air-hole array pattern. The light output power of the TAH-LED structure has a 55% enhancement compared with the conventional LED structure at 20 mA operation current. At 20 mA operation current, the forward voltage and peak electroluminescence wavelength of the TAH-LED were measured to be 3.09 V and 455.6 nm, respectively, similar to those of the conventional LED structure because the truncated-conical air-hole array pattern was fabricated around the mesa-edge region without affecting the current injection area with a top transparent contact layer. (C) 2012 The Japan Society of Applied Physic
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