| Popis: |
The light emitting diode (LED) is the dominant type of compound semiconductor device in terms of the epitaxial area of material produced as well as the number of devices fabricated and sold. Recent breakthroughs have resulted in dramatic performance increases for visible LEDs. Very high performance devices are commercially available using the AlGaInP materials system for red, orange and yellow and the InGaN system for green and blue. External quantum efficiencies greater than 10% are available for most colors, with greater than 20% having been achieved in red to orange. Currently, the luminous performance of LEDs exceeds that of traditional incandescent lamps for colors from red to green. As a result of these advances, LEDs are becoming competitive in applications such as large area signs, traffic signals and automobile lighting. By mixing red, blue and green LEDs or by using phosphor-converted blue or ultraviolet devices, the creation of white light can be achieved, opening up additional applications. A review of the applications for high-brightness LED technology will also be presented. |
