Optoelectronic devices based on nitride semiconductors

Volker Haerle 

OSRAM Opto Semiconductors GmbH, Wernerwerkstrasse 2, Regensburg D-93049, Germany

Abstract

Over the last ten years the importance of optoelectronic devices based on nitrides grew enormously due to their advantages compared to conventional light sources like incandescent and halogen light bulbs, which are mainly high lifetime, small size and meanwhile the higher wall plug efficiency. Ga(In,Al)N-compound semiconductors are suitable for light emitting devices like LEDs and Lasers due to their direct bandgap. The emission wavelength of the device is defined by the In-content in the GaInN-Quantum-Wells within a pn-junction. Thus, it is possible to realize light emission in the ultraviolet and almost the whole visible spectral range. By combining blue, green and red LEDs or blue LEDs with phosphorus for colour conversion a huge colour variation is possible including white.
At OSRAM Opto Semiconductors, blue LEDs are in production since 1997 starting predominantly for automotive interior illumination like dash boards. Up to now the application spectrum extended to communication (keypad- and LCD-backlighting and flash lights in mobile phones), all kinds of light signs (traffic signals, advertising neon writing,…), full colour displays and general lighting.
Besides this general overview over light generation and applications, this talk will address details concerning the technology of high brightness LED fabrication at OSRAM Opto Semiconductors and the brightness improvement over the last years. A special role plays the advanced Thinfilm-technology, which enables front emitting LEDs compared to the conventional volume emitting GaN-based LEDs on SiC- and Sappphire substrates. The main advantages of this technology are the linear scalability to bigger devices, high luminance and the possibility of on chip conversion. These advanced Power devices enable additional applications like automotive head lamps, compact light sources for projection, and a further growing market in general lighting in near future.

 

Presentation: invited oral at E-MRS Fall Meeting 2005, Plenary session, by Volker Haerle
See On-line Journal of E-MRS Fall Meeting 2005

Submitted: 2005-05-18 07:50
Revised:   2009-06-07 00:44