High brightness near‐ultraviolet resonant LEDs

Planar near‐ultraviolet 385 nm emitting resonant LEDs containing three quantum wells have been investigated as a function of the separation between the wells and a reflective and injecting metal mirror. The output power and far‐field extracted through the substrate of the LEDs depend on the precise positions of the wells with each well having a significant individual influence on these properties. A doubling of the output power is obtained when the wells are located around the antinode position of the standing wave while narrower far‐fields are obtained with other placement of the wells. A power of 0.4 mW into a numerical aperture of 0.5 is obtained for a current of 30 mA into a 50 μm diameter contact. Calibration of the growth rate along with accurate knowledge of the material properties of the semiconductor and metal mirrors is required for controlled and enhanced emission from planar UV LEDs. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)