Epitaxial growth of GaAs has been performed with diethylarsine (DEAs) to investigate its potential as a replacement of arsine. Triethylgallium (TEG) and trimethylgallium (TMG) were used as group‐III sources and carbon incorporation into the epilayers was compared. The growths were carried out under low‐pressure conditions (130 Pa–1.3 kPa) to avoid a gas‐phase reaction between the precursors. All epilayers exhibitedp‐type conductivity,and the main acceptor impurity was carbon. The lowest hole concentrations were ∼1016and ∼1017cm−3for TEG and TMG, respectively. The dependence of hole concentration on V/III ratio suggests that the carbon incorporation comes mainly from TMG and DEAs for the TMG/DEAs mixture, and from DEAs for the TEG/DEAs mixture. These results indicated that the contribution of the H atom from the As—H bond in DEAs on reduction of carbon incorporation was not enough to grow high‐purity GaAs.