No abstract

Data are presented on the operation of thin-film flip-chip InGaN∕GaN multiple-quantum-well light-emitting diodes (LEDs). The combination of thin-film LED concept with flip-chip technology is shown to provide surface brightness and flux output advantages over conventional flip-chip and vertical-injection thin-film LEDs. Performance characteristics of blue, white, and green thin-film flip-chip 1×1mm2 LEDs are described. Blue (∼441nm) thin-film flip-chip LEDs are demonstrated with radiance of 191mW∕mm2sr at 1A drive, more than two times brighter than conventional flip-chip LEDs. An encapsulated thin-film flip-chip blue LED lamp is shown to have external quantum efficiency of 38% at forward current of 350mA. A white lamp based on a YAG:Ce phosphor coated device exhibits luminous efficacy of 60lm∕W at 350mA with peak efficiency of 96lm∕W at 20mA and luminance of 38Mcd∕m2 at 1A drive current. Green (∼517nm) devices exhibit luminance of 37Mcd∕m2 at 1A.

Recent advances in the phosphors used for field emission displays (FEDs) are discussed. After reviewing the range of voltages and phosphors being used in first generation devices, the improved properties of future generation phosphors are reviewed. Specifically, next generation displays will require better low voltage efficiencies, chromaticity, saturation behavior, and maintenance. Possible routes to achieve these improvements are discussed. The improved understanding of the role of charging and surface recombination effects on cathodoluminescent intensity and efficiency is reviewed. An improved understanding of electron beam-stimulated surface chemical reaction effects on the degradation of phosphor is presented. It is concluded that recent research efforts have created a new level of understanding of FED phosphors, and this should lead to the necessary improvements in properties.

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.

Degradation of ZnS and Y2O2S cathodoluminescent (CL) phosphors has been studied at 1–4 keV using Auger electron spectroscopy simultaneous with CL. The data are consistent with an electron stimulated surface chemical reaction (ESSCR) which led to destruction of ZnS and formation of a surface nonluminescent ZnO layer as well as injection of oxygen point defects into the near-surface region. In the case of Y2O2S:Eu, the electron beam stimulated removal of S and formation of Y2O3:Eu in the presence of 1×10−6 Torr of oxygen. A model is presented which predicts that degradation by the ESSCR should increase with pressure in the vacuum, depend exponentially on electron dose, increase as the primary beam energy was reduced below 4 keV, and depend upon the type of gas present in the vacuum. These trends were demonstrated from the experimental data.