For GaAs grown by molecular beam epitaxy (MBE), predeposition of a sufficient amount of Sn on the substrate surface, which tends to segregate to the film surface during growth, can uniformly dope the subsequently grown overlayer. For example, GaAs grown on a substrate predeposited with ∼one monolayer of Sn, results in uniformlyn‐type doped overlayer with ∼200 nm thickness. Similar segregation effects also have been observed in GaAs doped withn‐type dopant Te andp‐type dopants, Mn, Fe and Cr. Based on this so‐called “predeposition doping” method, a laterally‐selectively doped GaAs layer can be grown on a surface which is repeatedly prepared by depositing each kind of the aforementioned dopant on an InAs passivated surface, followed by the selective etching to define its covered region, followed by the removal of InAs by thermal desorption. The latter requires the dopants to have low vapor pressures at the InAs desorption temperature. Finally, a GaAs layer with a lateralp‐njunction exhibiting excellent diode characteristics was grown to demonstrate this laterally‐selective doping MBE technique.