So far most kinetic Monte Carlo (kMC) simulations of heterogeneously catalyzed gas phase reactions were limited to flat crystal surfaces. The newly developed program MoCKA (Monte Carlo Karlsruhe) combines graph-theoretical and lattice-based principles to be able to efficiently handle multiple lattices with a large number of sites, which account for different facets of the catalytic nanoparticle and the support material, and pursues a general approach, which is not restricted to a specific surface or reaction. The implementation uses the efficient variable step size method and applies a fast update algorithm for its process list. It is shown that the analysis of communication between facets and of (reverse) spillover effects is possible by rewinding the kMC simulation. Hence, this approach offers a wide range of new applications for kMC simulations in heterogeneous catalysis.

We investigate the influence of chip size, substrate shaping and mounting techniques on the light extraction efficiency of large area InGaN‐LED chips grown on 6H‐SiC substrates. New techniques to achieve good light extraction for large chip areas are demonstrated and discussed. Applying these techniques to InGaN on SiC chips with 1 mm2 size, we generate 150 mW of blue light and 33 lm of white light at a forward current of 350 mA. For efficient light extraction from the chip and for good thermal coupling the chip is soldered up‐side down into a newly developed SMT package with a thermal resistance below 10 K/W.

We present brightness improvements of blue InGaN chips on SiC substrates. Chip shape, performance of the contacts, high structural quality of the InGaN quantum well layers are essential for an optical output as high as 9.5 mW at 470 nm and 20 mA. The external quantum efficiency is 18%. The light extraction out of the chip is increased to 55% as calculated by a ray trace simulation. This is the highest value ever reported on InGaN chips, which are conventionally mounted with epitaxial layers upside. The optimized chip side walls have vertical angles of 60. The reflectivity at the p-contact is increased to 90% for flat angles of 0 to 20 . An internal quantum efficiency of 32% is estimated from the values of light extraction and external quantum efficiency. The epitaxial layers are improved by optimizing the growth parameters of the quantum wells interfaces. Electrical losses are reduced by better interface quality of epitaxial layers and by an improved p-contact resistance of 10 --4 W cm 2 , respectively.Introduction Institutions for market analysis estimate the market of high brightness light emitting diodes (LEDs) to be about 1200 million US$. The share of InGaN products was increasing during the last few years. Today the InGaN share is expected to be 66%. The continous increase of brightness levels made possible new fields of applications. At the beginning of InGaN activities, optical output of blue InGaN LEDs was about 1.5 mW [1]. The brightness level was sufficient for indoor applications, only. In 1999, the output power broke through the lower limit for outdoor applications of 5 mW. In 2000, the best blue chips on sapphire reached optical power of 10 mW at 20 mA in a 5 mm lamp [2]. We now look at two different technologies of InGaN devices. At the beginning of the nineties, the InGaN technology was dominated by sapphire-based epitaxy. LED-chips with InGaN on SiC substrate were demonstrated not earlier than 1995. The SiC-based chips have a smaller size than sapphire chips, a true vertical current flow and an excellent stability against electrostatical discharge. These are the reasons that the SiC-based chips dominate the automotive applications. However, the first SiC-based chips did not reach the brightness level of sapphire-based chips due to the worse light extraction and worse epitaxial quality. Therefore, large area displays and outdoor applications were dominated by sapphire-based chips. In 2000, OSRAM developed the ATON technology [3], which pushed the output power of blue LEDs on SiC above the border of 5 mW at 470 nm and 20 mA [4][5][6]. The ATON technology improves the light extraction, which was patented and licensed to another company working on SiC [7].In this paper we will show optical output power of SiC-based chips of 9.5 mW at 470 nm and 20 mA, a level similar to sapphire based devices [2,8]. We present a

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