Reaction Mechanisms in the OMVPE Growth of GaAs and AlGaAs

The thermal decomposition of TMA, TMG, TEG and AsH3 has been investigated by QMS measurements. Hydrogen is used as a carrier gas. The order of the decomposition temperature is AsH3>TMG>TMA>TEG. The reactivity of H2 is stronger on TMA than on TMG, which results in a lower decomposition temperature of TMA than that of TMG. Hydrogen hardly reacts on TEG. The decomposition of TMA is enhanced with increasing AsH3, while it is suppressed by a small addition of AsH3 compared with TMA alone. This suppression originates in the interaction between TMA and AsH3, or adduct formation. The relative incorporation rate of Al in AlGaAs growth decreases at lower temperatures or lower V/III ratios. This behavior can be explained by adduct formation.