COMPUTATIONAL CHEMISTRY PREDICTIONS OF REACTION PROCESSES IN ORGANOMETALLIC VAPOR-PHASE EPITAXY

Quantitative understanding of reaction mechanisms in organometallic va por phase epitaxy (OMVPE) is critical for selection of precursors, des ign of equipment, and optimization of process conditions. Progress has been made in the simulation of fluid flow as well as heat and mass tr ansfer, but predictions of growth rates, alloy composition, and dopant incorporation are limited by the availability of thermodynamic and ki netic data for OMVPE precursors. Chemical kinetic experiments are expe nsive and difficult to perform, and the organometallic compounds being toxic and/or pyrophoric further complicates the situation. It is ther efore desirable to study OMVPE reactions from first principles, quantu m chemistry computations. We describe current quantum chemistry method s, Hartree-Fock and post-Hartree-Fock ab initio molecular orbital tech niques and density functional theory (DFT) methods, with emphasis on i ssues related to OMVPE applications. The primary examples in this revi ew are drawn from OMVPE applications, but studies on silicon chemistry are also included to illustrate important elements in simulation of v apor phase growth processes. Molecular structure and energy are report ed for trialkyl group LII species and group V hydrides by ab initio mo lecular orbital and density functional theory. The results are evaluat ed against experimental data Vibrational frequencies needed for calcul ation of thermochemical properties (e.g., Delta H and Delta S) at proc ess temperatures are also computed and compared to experimental data. The bimolecular reaction of methyl with arsine exemplifies the combine d use of quantum chemistry and transition state theory to predict a re action rate. A reaction mechanism for thermal decomposition of phosphi ne further demonstrates the use of these techniques. Lewis-acid-base a dduct reactions of group III and V precursors exemplifies the use of q uantum chemistry to evaluate adduct bond strengths and potential alkan e elimination reaction pathways. A study of thermochemical properties of bridging organometallic aluminum compounds serves to illustrate var iations in accuracy among different first principle methods. Overall, the selected examples demonstrate that computational chemistry techniq ues can provide useful insight into OMVPE chemical processes, but also that additional investigations are needed to establish which methods would be best for particular subsets of OMVPE chemistry.