High-purity AlGaAs has been grown using chemical beam epitaxy employing a new gallium precursor, triisopropylgallium . NEt(3) in combination with AlH3(NMe(2)Et). The materials exhibit low oxygen concentrations and excellent optical and electrical characteristics, comparable with the best materials grown using molecular beam epitaxy or metal-organic vapor phase epitaxy. The use of amine solvents and the complete absence of ethers from the precursors has important consequences for the growth of III-V alloys by CBE, as oxygen-containing solvents are known to lead to materials degradation.