Ga‐As‐In‐As superalloy has been grown by atomic epitaxy on InP substrates. This has been achieved by sequential exposure of the substrate to trimethylgallium, arsine, triethylindium, and arsine. The thickness of the deposited film is in excellent agreement with the predicted value based on the number of exposure cycles. These results demonstrate that atomic layer epitaxy offers the ultimate control for depositing thin films. The superalloy films have been characterized by transmission electron microscopy and photoluminescence.