Gas Phase and Surface Effects in the Thermal Decomposition of AsH3 and PH3 Studies by CARS

Abstract

Coherent anti-Stokes Raman Scattering (CARS) is used to study the thermal decomposition of AsH3 and PH3 related to metalorganic vapor phase epitaxy (MOVPE) of III/V compound semiconductors. Both in situ diagnostics and ex situ sampling experiments are considered. The decomposition temperatures obtained from in situ experiments (450–600 K) are much lower than those measured by ex situ techniques (900–1000 K). The ex situ data compare well to previously reported observations. The large difference in decomposition behaviour between the two measuring techniques also demonstrates the importance of in situ diagnostics and the difficulty in ex situ monitoring of MOVPE species concentrations. No change in AsH3 or PH3 decomposition behaviour is observed with the addition of TMG or TMI. Studies in an isothermal reactor demonstrate surface catalytic effects. Molecular hydrogen is detected as a decomposition product but at temperatures higher than those required to decompose ASH3. This is interpreted in terms of a mechanism involving subhydrides of arsenic.KeywordsDecomposition BehaviourIsothermal ReactorMetalorganic Vapor Phase EpitaxyAverage Linear VelocityHydride DecompositionThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.