Selective area epitaxy (SAE) of GaAs, AlAs and (AlGa)As by molecular beam epitaxy (MBE) was successfully achieved by employing periodic supply epitaxy (PSE) in which group III flux is sent in pulse under a continuous group V flux. Smooth and Bat surface was obtained in the window area on (001) and (111)B substrates and strong enhancement of selectivity was observed by increasing the ratio of the group III flux interruption time to the deposition time. However, the substrates of (110), (111)A and (411)A gave the layers with less smoothness. SAE of AlAs and (AlGa)As by PSE was conducted at 640 degrees C and complete selectivity was obtained by decreasing thr growth rate or partial growth rate of AlAs. It was found that in PSE of (AlGa)As, the Al Bur uniquely determines the selectivity and depleted zone width. PSE was applied to fabricate submicron structures. An array of lines with less than 0.5 mu m. in width has been successfully grown without any polycrystal deposits on the mask.