Epitaxial layers of nominally undoped GaAs have been grown by metalorganic chemical vapor deposition using liquid tertiarybutylarsine and triethylgallium.n‐type layers were obtained having total residual shallow acceptor concentrations of ∼1013cm−3and Hall mobilities comparable to those obtained with arsine and triethylgallium in the same reactor. Liquid‐nitrogen Hall mobilities up to 116 000 cm2/V s were observed.