In the present article we briefly review some materials research aspects related to ceramic phosphors and discuss both typical characteristics as well as unique features of such optical converters. Devices with more efficiency and/or higher luminous flux that are based on converting the pump light crucially enable the use of LEDs in white and single color illumination schemes for many applications. Advantages of generating white light with ceramics versus powder-in-silicone are discussed. High performance of single color conversion LEDs in terms of efficacy and external quantum efficiency for the visible region boost the output in data or home cinema projection and automotive signaling but more applications are appearing.

During the last years GaN‐technology has proven to fulfill the requirements of solid state lighting. Lighting requirements are mainly driven by brightness, operation voltage and lifetime. Brigthness is determined by internal efficiency as well as extraction efficiency whereas the ohmic losses determining the operating voltage are dominated by series resistance and contact resistance. Both, brightness and voltage, strongly depend on the device structure as well as the chip design. SiC based [1, 2] as well as Sapphire based LEDs [3] have proven their capability for high brightness devices, still suffering from various compromises such as cost, ESD‐stability, high series resistance etc. Recently OSRAM‐OS has demonstrated its newly developed product line based on the so called ThinGaN™ technology, a true thinfilm approach that overcomes most of the compromises mentioned. The technology allows highest brightness levels at lowest operating voltage, is scalable and supports all wavelengths. The devices act as true surface emitters with a lambertian emission pattern. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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At OSRAM Opto Semiconductors GaN based devices are grown using metalorganic vapor phase epitaxy (MOVPE) on SiC substrates. SiC as a substrate offers many advantages both from epitaxial and device processing point of view. For production on an industrial scale both a stable epitaxial process and a low cost chip technology had to be developed. By using an optimized GaInN MQW for the active region and an improved chip technology as well as package design leading to a better light extraction the LED optical output at 460 nm exceeds now 7 mW at 20 mA in a 5 mm radial lamp. By optimizing buffer growth and GaInN active region, p-and n-contacts, grinding and polishing processes as well as facet cleaving the first European GaN based violet laser diode could be realized. The device had an emission wavelength of 420 nm, a threshold current density of less than 17 kA/cm 2 at 25 V and operated under pulsed current injection at room temperature.