Morphological evolution and properties of epitaxial GaN nanowall network grown on c-sapphire

Abstract

The technological advancement to obtain high brightness sources is an ongoing and an important aspect of human development. From lighting the first fire millenia ago, mankind has been on a never ending quest to better technologies for brighter lighting sources. Since energy conservation is a big environmental concern, the world has most recently seen a gradual phasing out of the most popular incandescent light bulbs and the evolution of solid state lighting, a technology that utilizes the emission from semiconductor light emitting diodes (LEDs) to convert electricity to light in an efficient way. For comparison between various devices, lighting is typically quantified by its light output per unit energy put in. A typical measure of light output is “lumen”, defined as a unit of luminous flux equal to the light emitted in a unit solid angle by a uniform point source of one candela (cd) intensity. Candela is the base unit of luminous intensity in the international system of units (SI) that is equal to the luminous intensity in a given direction of a source which emits monochromatic radiation of frequency 540x1012 hertz and has a radiation intensity in that direction of 1 683 watt per unit solid angle. Incandescent bulbs typically have an intensity of about 1200-1800 lumens while natural sunlight is about 1000-6000 lumens.