We developed a green-emitting phosphor Sr 3 Si 13 Al 3 O 2 N 21 :Eu 2þ that is highly luminescent under excitation by blue light. It shows a highly efficient green luminescence whose external quantum efficiency reaches 67% for 460 nm excitation, and has small thermal quenching. Using this phosphor, we obtained white light-emitting diodes (LEDs) whose luminous efficacy and color rendering index R a at 5330 K are 62 lm/W and 87, respectively. These features show that this green-emitting phosphor has high potential for application to white LEDs.

We have successfully developed a white light-emitting diode (LED) for a wide-color-gamut backlight composed of a green-emitting phosphor Sr3Si13Al3O2N21:Eu2+ combined with a blue LED and a red-emitting phosphor CaAlSiN3:Eu2+. This white LED showed a discrete spectrum with distinct separation of red, green, and blue primary colors due to a narrow emission band of around 525 nm for the green phosphor. 94.2% of the wide color gamut of the National Television System Committee standard was attained by applying typical color filters of LCDs. The power LED module composed of 16 of these white LEDs revealed their excellent power dependence. The LED is expected to replace cold cathode fluorescent lamp (CCFL), and find a suitable application as a backlight in large-scale LCDs for in-vehicle use or for flat-panel television sets.

Achievement of lowresistivity ptype ZnSe and the role of twinning J. Appl. Phys. 65, 4859 (1989); 10.1063/1.343198 High quality ZnSe films grown by low pressure metalorganic vapor phase epitaxy using methylalkyls Appl. Phys. Lett. 50, 1065 (1987); 10.1063/1.97971Conduction mechanism in lowresistivity ntype ZnSe prepared by organometallic chemical vapor deposition

A series of photoluminescent Ce 3+ doped samples with compositions close to Sr 2 Si 7 Al 3 ON 13 :Ce have been studied by neutron powder diffraction to determine the Si 4+ /Al 3+ and N 3À /O 2À site ordering.Contrary to a commonly held assumption that the edge sharing tetrahedral sites in this structure are occupied exclusively by Al 3+ , we find a partial occupancy of Al 3+ on these site but also an unexpected preference for Al 3+ to occupy 2 other tetrahedral sites which are only corner sharing. From the crystal structures and local structures, as determined by pair distribution function (PDF) analysis, we also find evidence for alternating Si-Al site ordering within the edge sharing chains as well as dimerization of the Si 4+ and Al 3+ cations within these chains. The O 2À are found to be partially ordered onto 2 of the anion sites, although small amounts of O 2À are found on other sites as well. The cation and anion ordering found by neutron diffraction is supported by theoretical calculations. Understanding cation and anion ordering is essential for optimizing the photoluminescence properties of this promising class of phosphor materials.

We developed a simulation method for designing the luminescence profiles of white light-emitting diodes (LEDs) with multicolor phosphor blend. By taking into account the effect of the light scattering by phosphor particles as well as the reabsorption effect by phosphor species, we found a model of white LEDs to calculate the light output as a function of various parameters such as the thickness of the resins, the concentration of phosphors, and the spatial distribution of phosphor particles. This method is widely applicable to phosphor-based white LEDs with either blue or UV excitation.