Data are presented on high-power AlGaInN flip-chip light-emitting diodes (FCLEDs). The FCLED is “flipped-over” or inverted compared to conventional AlGaInN light-emitting diodes (LEDs), and light is extracted through the transparent sapphire substrate. This avoids light absorption from the semitransparent metal contact in conventional epitaxial-up designs. The power FCLED has a large emitting area (∼0.70 mm2) and an optimized contacting scheme allowing high current (200–1000 mA, J∼30–143 A/cm2) operation with low forward voltages (∼2.8 V at 200 mA), and therefore higher power conversion (“wall-plug”) efficiencies. The improved extraction efficiency of the FCLED provides 1.6 times more light compared to top-emitting power LEDs and ten times more light than conventional small-area (∼0.07 mm2) LEDs. FCLEDs in the blue wavelength regime (∼435 nm peak) exhibit ∼21% external quantum efficiency and ∼20% wall-plug efficiency at 200 mA and with record light output powers of 400 mW at 1.0 A.

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).

High power light emitting diodes (LEDs) continue to increase in output flux with the best III‐nitride based devices today emitting over 150 lm of white, cyan, or green light. The key design features of such products will be covered with special emphasis on power packaging, flip‐chip device design, and phosphor coating technology. The high‐flux performance of these devices is enabling many new applications for LEDs. Two of the most interesting of these applications are LCD display backlighting and vehicle forward lighting. The advantages of LEDs over competing lighting technologies will be covered in detail.

Optical cavity effects have a significant influence on the extraction efficiency of InGaN/GaN quantum-well-heterostructure flip-chip light-emitting diodes (FCLEDs). Light emitted from the quantum well (QW) self-interferes due to reflection from a closely placed reflective metallic mirror. The interference patterns couple into the escape cone for light extraction from the FCLED. This effect causes significant changes in the extraction efficiency as the distance between the QW and the metallic mirror varies. In addition, the radiative lifetime of the QW also changes as a function of the distance between the QW and the mirror surface. Experimental results from packaged FCLEDs, supported by optical modeling, show that a QW placed at an optimum distance from the mirror provides a ∼2.3× increase in total light output as compared to a QW placed at a neighboring position corresponding to a minimum in overall light extraction.

We have demonstrated hole injection through a tunnel junction embedded in the GaN-based light emitting diode structure. The tunnel junction consists of 30 nm GaN:Si++ and 15 nm InGaN:Mg++ grown on a GaN–InGaN quantum well heterostructure. The forward voltage of the light emitting diode, including the voltage drop across the reverse-biased tunnel junction, is 4.1 V at 50 A/cm2, while that of a standard light emitting diode with a conventional contact structure is 3.5 V. The light output of the diode with the tunnel junction is comparable to that of the standard device. This tunnel junction eliminates the need for a highly resistive p-AlGaN cladding layer in short-wavelength laser diodes and the semi-transparent electrode required for current spreading in conventional GaN-based light emitting diodes.