Publications

Abstract not provided.

This SAND report is the final report on Sandia's Grand Challenge LDRD Project 27328, 'A Revolution in Lighting -- Building the Science and Technology Base for Ultra-Efficient Solid-state Lighting.' This project, which for brevity we refer to as the SSL GCLDRD, is considered one of Sandia's most successful GCLDRDs. As a result, this report reviews not only technical highlights, but also the genesis of the idea for Solid-state Lighting (SSL), the initiation of the SSL GCLDRD, and the goals, scope, success metrics, and evolution of the SSL GCLDRD over the course of its life. One way in which the SSL GCLDRD was different from other GCLDRDs was that it coincided with a larger effort by the SSL community - primarily industrial companies investing in SSL, but also universities, trade organizations, and other Department of Energy (DOE) national laboratories - to support a national initiative in SSL R&D. Sandia was a major player in publicizing the tremendous energy savings potential of SSL, and in helping to develop, unify and support community consensus for such an initiative. Hence, our activities in this area, discussed in Chapter 6, were substantial: white papers; SSL technology workshops and roadmaps; support for the Optoelectronics Industry Development Association (OIDA), DOE and Senator Bingaman's office; extensive public relations and media activities; and a worldwide SSL community website. Many science and technology advances and breakthroughs were also enabled under this GCLDRD, resulting in: 55 publications; 124 presentations; 10 book chapters and reports; 5 U.S. patent applications including 1 already issued; and 14 patent disclosures not yet applied for. Twenty-six invited talks were given, at prestigious venues such as the American Physical Society Meeting, the Materials Research Society Meeting, the AVS International Symposium, and the Electrochemical Society Meeting. This report contains a summary of these science and technology advances and breakthroughs, with Chapters 1-5 devoted to the five technical task areas: 1 Fundamental Materials Physics; 2 111-Nitride Growth Chemistry and Substrate Physics; 3 111-Nitride MOCVD Reactor Design and In-Situ Monitoring; 4 Advanced Light-Emitting Devices; and 5 Phosphors and Encapsulants. Chapter 7 (Appendix A) contains a listing of publications, presentations, and patents. Finally, the SSL GCLDRD resulted in numerous actual and pending follow-on programs for Sandia, including multiple grants from DOE and the Defense Advanced Research Projects Agency (DARPA), and Cooperative Research and Development Agreements (CRADAs) with SSL companies. Many of these follow-on programs arose out of contacts developed through our External Advisory Committee (EAC). In h s and other ways, the EAC played a very important role. Chapter 8 (Appendix B) contains the full (unedited) text of the EAC reviews that were held periodically during the course of the project.

Magnesocene (biscyclopentadienylmagnesium) is a common precursor used for the p-type doping of GaN and other group III nitride materials. Unfortunately, difficulties remain with predictably controlling the incorporation of Mg during metal organic chemical vapor deposition (MOCVD) film growth, which often exhibits poorly understood 'memory effects.' Although the formation of a reaction product between magnesocene and ammonia has been previously speculated, one has never been experimentally isolated or identified. We have spectroscopically observed and identified, for the first time, the adducts formed between magnesocene and ammonia. Density functional theory (DFT) quantum chemistry calculations have also been performed on the system to determine the structures and energetics of the reaction products. It was found that ammonia can form condensable Lewis acid-base complexes with magnesocene in both 1:1 and 2:1 ratios (i.e., NH{sub 3}-MgCp{sub 2} and (NH{sub 3}){sub 2}-MgCp{sub 2}) via nucleophilic attack of NH{sub 3} at the positively charged Mg center of MgCp{sub 2}. Adduct formation is reversible, and the 1:1 and 2:1 products can be converted to one another by controlling the NH{sub 3} partial pressure. The formation and condensation of both adducts at room temperature is the probable parasitic source that leads to many of the observed Mg incorporation difficulties during the p-type doping of group III nitride materials.

Using in situ laser light scattering, we have observed gas-phase nanoparticles formed during AlN, GaN and InN OMVPE. The response of the scattering intensity to a wide range of conditions indicates that the AlN parasitic chemistry is considerably different from the corresponding GaN and InN chemistry. A simple CVD particle-growth mechanism is introduced that can qualitatively explain the observed particle size and yields a strong residence time dependence. We also used FTIR to directly examine the reactivity of the metalorganic precursors with NH{sub 3} in the 25-300 C range. For trimethylaluminum/NH{sub 3} mixtures a facile CH{sub 4} elimination reaction is observed, which also produces gas-phase aminodimethylalane, i.e. Al(CH{sub 3}){sub 2}NH{sub 2}. For trimethylgallium and trimethylindium the dominant reaction is reversible adduct formation. All of the results indicate that the AlN particle-nucleation mechanism is predominately of a concerted nature, while the GaN and InN particle-nucleation mechanisms involve homogeneous pyrolysis and radical chemistry.