Low‐pressure metalorganic vapor‐phase epitaxy was adopted to grow AlGaAs epitaxial films by using triethyl‐gallium, trimethyl‐aluminum, and AsH3as the Ga, Al, and As sources, respectively. Growth rate, incorporation rates, and AlAs solid composition versus growth temperature have been investigated by electron probe microanalysis with the following results: the growth rate, the AlAs fraction in AlGaAs, and the Al and Ga incorporation rates increase with increasing growth temperature under reduced pressure. The Al incorporation rate increases more quickly than that of the Ga in AlGaAs. The above results are consistent with one another.