Trimethylamine alane (TMAAl) has been demonstrated to be a superior Al precursor for growth of AIGaAs by metal-organic molecular beam (MOMBE). TMAA1 reduces both carbon and oxygen contamination relative to the standard Al source, triethylaluminum (TEA1). However, AlGaAs grown with TMAAl still shows a residual oxygen background of ∼2 × 1018 cm−3 when used with triethylgallium (TEGa) and either As4 or ASH3. This background is independent of Al mole fraction and is due primarily to alkoxides in the TEGa. AIGaAs grown with TMAAl and elemental Ga contains oxygen at levels commonly obtained in MBE, −2 × 1017 cm-3. While an oxygen level of −2 × 1018 cm-3 is not desirable, we have found that most of this impurity is electrically inactive as evidenced by room temperature photoluminescence and n-type dopant activation. In light of this, we have assessed the applicability of AlGaAs grown with TMAAl to the fabrication of high-speed GaAs/AIGaAs devices. The source is found to be suitable for structures like the heterojunction bipolar transistor.