InGaN light emitting diodes (LED) structure with an embedded 1/4λ-stack nanoporous-GaN/undoped-GaN distributed Bragg reflectors (DBR) structure have been demonstrated. Si-heavily doped GaN epitaxial layers (n+-GaN) in the 12-period n+-GaN/u-GaN stack structure are transformed into low refractive index nanoporous GaN structure through the doping-selective electrochemical wet etching process. The central wavelength of the nanoporous DBR structure was located at 442.3 nm with a 57 nm linewidth and a 97.1% peak reflectivity. The effective cavity length (6.0λ), the effective penetration depth (278 nm) in the nanoporous DBR structure, and InGaN active layer matching to Fabry-Pérot mode order 12 were observed in the far-field photoluminescence radiative spectra. High electroluminescence emission intensity and line-width narrowing effect were measured in the DBR-LED compared with the non-treated LED structure. Non-linear emission intensity and line-width reducing effect, from 11.8 nm to 0.73 nm, were observed by increasing the laser excited power. Resonant cavity effect was observed in the InGaN LED with bottom nanoporous-DBR and top GaN/air interface.

InGaN light emitting diodes (LED) structure with an embedded 1/4λ-stack nanoporous-GaN/undopedGaN distributed Bragg reflectors (DBR) structure have been demonstrated. Si-heavily doped GaN epitaxial layers (n + -GaN) in the 12-period n + -GaN/u-GaN stack structure are transformed into low refractive index nanoporous GaN structure through the doping-selective electrochemical wet etching process. The central wavelength of the nanoporous DBR structure was located at 442.3 nm with a 57 nm linewidth and a 97.1% peak reflectivity. The effective cavity length (6.0λ), the effective penetration depth (278 nm) in the nanoporous DBR structure, and InGaN active layer matching to Fabry-Pérot mode order 12 were observed in the far-field photoluminescence radiative spectra. High electroluminescence emission intensity and line-width narrowing effect were measured in the DBR-LED compared with the non-treated LED structure. Non-linear emission intensity and line-width reducing effect, from 11.8 nm to 0.73 nm, were observed by increasing the laser excited power. Resonant cavity effect was observed in the InGaN LED with bottom nanoporous-DBR and top GaN/air interface.Gallium nitride (GaN) materials have considerable in optoelectronic devices such as light-emitting diodes (LEDs), laser diodes (LD) 1 , and vertical cavity surface emitting lasers (VCSEL) 2 . High reflectivity distributed Bragg reflectors (DBR) structure, short cavity thickness 3-5 , high transparence conductive layer, efficient transverse current spreading, small current confinement aperture, and resonant cavity controled in the nitride VCSEL need to be improved. Leonard et al. reported on violet nonpolar III-nitride VCSELs with a tunnel junction intracavity contact 6 and an Al ion implanted aperture 7 . The epitaxial AlGaN/GaN stack 8,9 and AlN/GaN stacks 10,11 structures had been reported for the bottom epitaxial DBRs in GaN-based VCSEL devices. Large lattice mismatch and low refractive index different of the stack structures are the challenges for the epitaxial DBR structures with long epitaxial growth time. The AlInN/GaN DBR structure 12,13 is lattice matched to GaN material, but the growth of AlInN layer remains a challenge in InGaN-based LED structures. To realize the high reflectivity with less pairs of stack structure, the air-gap/GaN DBR structures with large refractive index different had been fabricated through selectively anodized processe 14,15 , and thermal decomposition techniques [16][17][18] . But, the low mechanical strength and the tiny high reflective area remains a challenge for the photonic device fabrication. Plawsky et al. 19 . reported the nanoporous material for the photonics through the evaporation induced self-assembly process and oblique or glancing angle deposition. The resonant cavity effect of III-nitride thin-film flip-chip light-emitting diodes with anatase TiO 2 microsphere array were reported 20 . Nanoporous GaN material has been reported as an effective low refractive index for the DBR structure applications [21][22][23] .In this pa...

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.

InGaN-based light emitting diodes (LEDs) were embedded by an insulated disk-array gallium oxide (Ga(2)O(3)) pattern structure that was formed through a photoelectrochemical oxidation process on a GaN layer. A 4-mu m-diameter native Ga(2)O(3) pattern with a top air-void structure was observed in the lower undoped GaN layer acting as a lateral overgrowth mask and as a light scattering center. In the patterned-Ga(2)O(3) LED structure (PGO-LED), the light output power had an approximate 28% enhancement when compared to a conventional LED at 20 mA. In the PGO-LED structure, the lower piezoelectric field and the slightly higher internal quantum efficiency in the InGaN active layers were both measured through a bias-dependent and temperature-dependent microphotoluminescence measurement. The LED structure consists of Ga(2)O(3) disk-array patterns with top air-void structures that increase external quantum efficiency for nitride-based LED applications

The interfacial reactions between electroplated Ni-yCo alloy layers and Sn(Cu) solders at 250 degrees C are studied. For pure Co layers, CoSn(3) is the only interfacial compound phase formed at the Sn(Cu)/Co interfaces regardless of the Cu concentration. Also, the addition of Cu to Sn(Cu) solders has no obvious influence on the CoSn(3) compound growth at the Sn(Cu)/Co interfaces. For Ni-63Co layers, (Co,Ni,Cu)Sn(3) is the only interfacial compound phase formed at the Sn(Cu)/Ni-63Co interfaces. Unlike in the pure Co layer cases, the Cu additives in the Sn(Cu) solders clearly suppress the growth rate of the interfacial (Co,Ni,Cu)Sn(3) compound layer. For Ni-20Co layers, the interfacial compound formation at the Sn(Cu)/Ni-20Co interfaces depends on the Cu content in the Sn(Cu) solders and the reflow time. In the case of high Cu content in the Sn(Cu) solders (Sn-0.7Cu and Sn-1.2Cu), an additional needle-like interfacial (Ni(x),Co(y),Cu(1-x-y))(3)Sn(4) phase forms above the continuous (Ni(x),Cu(y),Co(1-x-y))Sn(2) compound layer. The Ni content in the Ni-yCo layer can indeed reduce the interfacial compound formation at the Sn(Cu)/Ni-yCo interfaces. With pure Sn solders, the thickness of the compound layer monotonically decreases with the Ni content in the Ni-yCo layer. As for reactions with the Sn(Cu) solders, as the compound thickness decreases, the Ni content in the Ni-yCo layers increases