PERIODIC SUPPLY EPITAXY - A NEW APPROACH FOR THE SELECTIVE-AREA GROWTH OF GAAS BY MOLECULAR-BEAM EPITAXY

Selective growth of GaAs on a GaAs substrate with a SiO2 patterned mask has been carried out by molecular beam epitaxy at 630 degrees C, using molecular beams of Ga and As-4 as sources and employing a periodic supply epitaxy technique for the first time. The GaAs crystalline nuclei deposited on the mask surface are decomposed and the atoms adsorbed on the mask surface are evaporated or allowed to migrate until they are captured by the single crystalline epitaxial layer. A wide depleted zone is then formed and the polycrystals of GaAs are located beyond this area. The surface migration is shown to influence drastically the thickness of the grown layer. The epitaxial layer obtained is flat and smooth even for the (001) substrates, since the lateral flux prevents the decomposition of GaAs on the free surface of the epitaxial layer. The growth technique is discussed in details, together with an analysis of the important parameters for the selective growth by periodic supply epitaxy.