Heteroepitaxy of GaAs on Si and Ge using alternating, low-energy ion beams

Crystalline GaAs films have been grown epitaxially on silicon and germanium substrates at 400 °C by direct deposition of alternating 69Ga and 75As layers from electromagnetically switched low-energy ion beams. Positive gallium and arsenic ions were extracted simultaneously from a single ion source and mass analyzed prior to deceleration to a controlled deposition energy of 30 or 40 eV. Atomic layers of gallium and arsenic were deposited alternately by switching the analyzing magnetic field repeatedly to select either the 69Ga+ or 75As+ species. The structure and composition of the resulting layers have been characterized by cross-section transmission electron microscopy and ion channeling/backscattering spectrometry. The best crystal quality was obtained for a GaAs layer deposited on Ge using a 30 eV beam. This layer gave an ion channeling minimum yield of ≊6%. These results demonstrate the feasibility of growing isotopically pure, single-crystal compound semiconductor layers at relatively low temperatures by deposition from alternating, fully ionized, low-energy beams.