CARBON INCORPORATION IN GAAS AND ALGAAS GROWN BY MOMBE USING TRIMETHYLGALLIUM

In spite of the attention that growth of GaAs from trimethylgallium (TMGa) by MOMBE has received, some uncertainty exists as to the nature of the carbon incorporation process. Specifically, it is unclear what reactions control the removal of methyl radicals from the growth surface, and whether these reactions can be influenced by the addition of other species such as hydrogen. In this paper, the role of hydrogen has been investigated by introducing molecular hydrogen as well as hydrogen bonded Group III and Group V sources. None of the hydrogen sources were found to significantly reduce the carbon background, through a small amount of passivation of the carbon acceptor was observed due to incorporation of hydrogen from incompletely dissociated CH3. Significant reduction in the carbon level is observed with increasing V/III ratio. Therefore, it appears that the carbon removal process is dominated by formation of (CH3)(x)As species rather than by formation of CH4. The growth kinetics of AlGaAs have also been examined and the data suggests that carbon incorporation in growth from TMGa is due to incorporation of (CH3)(x)Ga rather than adsorbed CH3 radicals.