GaAs was grown by the atomic layer epitaxy (ALE) technique by means of the alternate supply of trimethylgallium for 1 s and arsine (AsH 3) with photo irradiation at 530°C. The substrate surface was irradiated by an infrared lamp in the first half of the AsH 3 feed time. The carrier concentration in the ALE layer grown with irradiation for 4 s at 3 W/cm 2 during the 7 s AsH 3 feed time was reduced to 9 × 10 15 cm −3, which was one thirtieth as low as that without irradiation. The emission intensity associated with carbon impurity in photo-luminescence spectra decreased with the increase of light intensity.