High-power truncated-inverted-pyramid (AlxGa1−x)0.5In0.5P/GaP light-emitting diodes exhibiting >50% external quantum efficiency

Abstract

A truncated-inverted-pyramid (TIP) chip geometry provides substantial improvement in light extraction efficiency over conventional AlGaInP/GaP chips of the same active junction area (∼0.25 mm2). The TIP geometry decreases the mean photon path-length within the crystal, and thus reduces the effects of internal loss mechanisms. By combining this improved device geometry with high-efficiency multiwell active layers, record-level performance for visible-spectrum light-emitting diodes is achieved. Peak efficiencies exceeding 100 lm/W are demonstrated (100 mA dc, 300 K) for orange-emitting (λp∼610 nm) devices, with a peak luminous flux of 60 lumens (350 mA dc, 300 K). In the red wavelength regime (λp∼650 nm), peak external quantum efficiencies of 55% and 60.9% are measured under direct current and pulsed operation, respectively (100 mA, 300 K).

Finite-Difference Time-Domain Modeling of Periodic and Disordered Surface Gratings in AlInSb Light Emitting Diodes With Metallic Back-Reflectors

“…The antinode factor, , varies between 0 and 4 depending on the location of the source (periodic with ). For a single source with a metal mirror the peaks in occur at (4) where is any odd integer. However, this enhancement assumes a single point source, or localized set of sources such as would be found in a single quantum well.…”

“…In combination these effects lead to extraction efficiencies of the order of [2]. Many methods have been proposed to overcome this fundamental limitation, including adding a metallic rear reflector to the substrate side of the device [3], employing non rectangular parallelepiped chip geometries [4], [5], resonant-cavity devices [6], [7], lens immersion [8], surface patterning [9], surface roughening [10], [11], and two-dimensional surface relief diffraction gratings [12]- [15].…”

Solid‐state lighting

“…Given reasonable progress in green LEDs, we expected to reach 50 lm/W by 2010 with the color mixing approach. Further improvements to 150 lm/W were plausible considering the then-recent results [1] on red LEDs. With a 50 lm/W performance for white, SSL could attack the low hanging fruits of incandescent and halogen lamps.…”

“…Even more important: the wall-plug conversion efficiency for red LEDs had reached 53 % [1]; the quantum efficiency of blue LEDs had reached ~12 % at useful ~30 A/ cm2 current densities; and wall-plug efficiencies of LED-like vertical-cavity surface emitting lasers in the infrared had reached > 50 % [2]. Progress was such that the possibility that LED-based white lighting (or solid-state lighting, SSL) might someday compete favorably with traditional white lighting for general illumination began to be taken seriously, along with the possibility of massive savings in the energy consumption for lighting.…”

Raman measurements in water using a high‐power light‐emitting diode

“…1 To date, AlGaInP materials system-based LEDs emit in the red to amber spectral region with high efficiency approaching 60%. 2 Green to near-UV AlInGaN LEDs exhibit high optical power reaching 0.5 W. 3 High power, very stable and low-noise output, simple means of electronic modulation, long lifetimes, durability and low cost have stimulated the development of LED-based techniques for fluorescence excitation, 4 fluorescence lifetime measurements in the time 5 and frequency 6 domains, photoreflectance 7 and anti-Stokes luminescence stimulation. 8 Here we report on an LED-based Raman measurement technique that became feasible because of high spectral power density of the emission from advanced LEDs.…”