Abstract
The Gallium/Indium Nitride material system has changed the paradigm for efficient lighting after the first realization of high efficient blue LEDs in the 1990s [1]. This success was based on the realization of p-doped nitride material by activation Mg-acceptors through thermal annealing. At the same time, the number of other impurities and defects had to be limited during the growth of the devices using and proper is a wide band gap semiconductor material that is has received considerable interest due its favorable thermal, electrical, and optical properties, which make it an ideal material for applications in solid state lighting Organo-metallic Vapor Phase Epitaxy (OMVPE). In particular carbon and oxygen are problems in this technique. While significant progress has been achieved in moving the emission wavelength to longer wavelength by increasing the In content, the red color remains a challenge in this approach. In more recent years, an alternative approach has been developed by using Eu ion doping, which produces sharp emission lines at 620nm and enable LED structure with efficiency close to 1% and active layers with very good emission properties [2]. The key to this success was the realization that the europium ion needs to be placed close to a donor and/or an acceptor through proper defect engineering [3]. However, the commonly used sources that are used in in-situ doping contain oxygen and hence may deteriorate the device long-term reliability. We will report on the challenges of using oxygen-free Eu-sources and how they can be overcome.
© 2015 IEEE
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