Light-emitting Characteristics Research Articles

Kinetic model for degradation of light-emitting diodes

We present a kinetic model for the optical output degradation of light-emitting diodes based on the carrier-recombination enhanced defect motion. Our model leads to analytical solutions and universal curves for the optical output power and the defect density as a function of the normalized aging time with the initial quantum efficiency as the determining parameter. The theoretical results explain very well the time dependence of the II-VI light-emitting diodes under constant current aging condition. The faster aging rate with increasing bias current or temperature is also investigated both experimentally and theoretically, resulting in a very good agreement. Our model provides a quantitative description of the light-emitting diode aging characteristics for compound semiconductors in the presence of electron-hole recombination-enhanced defect generation.

Monte Carlo simulation of light-emitting diode light-extraction characteristics

We employ a Monte Carlo ray-tracing technique to model light-extraction characteristics of light-emitting diodes. By keeping track of the various processes that photons can encounter in a packaged LED, consisting of a semiconductor chip, a reflector dish, and an epoxy magnifying lens, our model can provide valuable information for LED design. The simulations can be performed very effectively on modern workstations. Preliminary results from a sample parametric study indicate that, with some refinement, our method could be used as a computer-aided design tool for optimizing light-extraction efficiencies and for designing LED spatial emission characteristics.

Light diode sound pressure transducer

The development of optoelectronics and the perfection of light guide, semiconductor laser and light-emitting diodes, and photodetector and other component characteristics are due to the creation of fiber optic transducers (FT) of sound [1-3]. Compared with traditional piezoelectric and electric acoustic transducers, the FT have high interference-immunity, sufficient sensitivity, small dimensions, are explosion-proof, reliable, and can be connected directly to fiber-optic information transmission lines.

Cathodoluminescence of Ga2(S1-xTex)3 Crystals and Films

In a solid solution Ga2(S1-xTex)3 prepared by an improved method, a uniform and intense cathodoluminescence is observed over the entire polycrystalline sample. The optimum composition for an intense luminescence is found to be x∼0.25. The composition dependence of an optical energy gap and the luminescence spectrum of the sample are obtained. Thin films are grown on Si substrate and their light-emitting characteristics are also measured. Composition dependence of emission intensity may be attributed to the fact that the sample is a mixture of a crystal with a tetragonal structure and an α-Ga2S3 crystal in the composition range 0<x<0.20.

The Performance of Color-Television Picture-Tube Phosphor Screens

Over the years, color picture tubes have been greatly improved in light-output performance while their ability to reproduce color has remained as good as or superior to other color-reproduction systems such as printing and color photography. This paper reviews the light-emitting characteristics of many of the phosphors that have been developed for color television, and presents the luminance and color-gamut potential of several tri-color combinations. A color-difference scale for use in color television is suggested and applied to the color-shift phenomenon in red zinc cadmium sulfide phosphor. Color coordinates are presented for twenty common objects and data are given on the desaturation effects of ambient illumination.