Knowledge Bank

Lewis acid-base concept predicts the initial formation of a 1:1 molecular adduct between trimethylgallium and arsine, which are gaseous precursors for the chemical vapor deposition of the semiconductor gallium arsenide. Isolation and characterization of this $(CH_{3}){3}Ga\cdot AsH{3} $ adduct for the first time using infrared matrix isolation technique showed that it has an effective symmetry of $C3v$. The corresponding adduct of phosphine with trimethylgallium has also been isolated and characterized using this technique. In addition, results of gas-phase studies indicate that both adducts may exist in the gas phase. Subsequent 193 nm photolysis of the ${(CH_{3})}{3}Ga\cdot AsH{3} $ adduct shows that an eliminated methyl radical abstracts a hydrogen to form methane and probably $(CH3)2Ga\cdot AsH2$. The photolysis of ${(CH_{3})}_{3}Ga $ at 193 nm has also been studied and results strongly indicate the production of dimethylgallium and methyl radicals.