The performance of III‐nitride based high‐power light emitting diodes (LEDs) is reviewed. Direct color high‐power LEDs with 1 × 1 mm2 chip size in commercial LUXEON® Rebel packages are shown to exhibit external quantum efficiencies at a drive current of 350 mA ranging from ∼60% at a peak wavelength of ∼420 nm to ∼27% at ∼525 nm. The short wavelength blue LED emits ∼615 mW at 350 mA and >2 W at 1.5 A. The green LED emits ∼110 lm at 350 mA and ∼270 lm at 1.5 A. Phosphor‐conversion white LEDs (1 × 1 mm2 chip size) are demonstrated that emit ∼126 lm of white light when driven at 350 mA and 381 lm when driven at 1.5 A (Correlated Color Temperature, CCT ∼ 4700 K). In a similar LED that employs a double heterostructure (DH) insign instead of a multi‐quantum well (MQW) active region, the luminous flux increases to 435 lm (CCT ∼ 5000 K) at 1.5 A drive current. Also discussed are experimental techniques that enable the separation of internal quantum efficiency and extraction efficiency. One technique derives the internal quantum efficiency from temperature and excitation‐dependent photoluminescence measurements. A second technique relies on variable‐temperature electroluminescence measurements and enables the estimation of the extraction efficiency. Both techniques are shown to yield consistent results and indicate that the internal quantum efficiency of short wavelength blue (λ ∼ 420 nm) high‐power LEDs is as high as 71% even at a drive current of 350 mA. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Data are presented showing that Zn diffusion into an AlAs-GaAs superlattice (41 Lz∼45-Å GaAs layers, 40 LB∼150-Å AlAs layers), or into AlxGa1−xAs-GaAs quantum-well heterostructures, increases the Al-Ga interdiffusion at the heterointerfaces and creates, even at low temperature (<600 °C), uniform compositionally disordered AlxGa1−xAs. For the case of the superlattice, the diffusion-induced disordering causes a change from direct-gap AlAs-GaAs (Eg∼1.61 eV) to indirect-gap AlxGa1−xAs (x∼0.77, EgX∼2.08 eV).

The feasibility of wafer bonding 50-nm diameter wafers consisting of GaP-AlGaInP light-emitting diode epitaxial films to GaP substrates is demonstrated. Wafer bonding over the entire wafer area is achieved while maintaining optical transparency and low-resistance electrical conduction at the wafer-bonded interface. Using this technique, visible-spectrum transparent-substrate GaP-AlGaInP/GaP light emitting diodes (LEDs) are fabricated across an entire 50-mm wafer with typical operating voltages <2.1 V at 20 mA and twice the flux of absorbing-substrate GaP-AlGaInP/GaAs LEDs. This large-area wafer-bonding method is further shown to be capable of producing very high efficiency emitters, with an external quantum efficiency of 23.7% (300 K, 20 mA, dc) at 635.6 nm.