EPITAXIAL-GROWTH AND CHARACTERIZATION OF DYP GAAS, DYAS/GAAS, AND GAAS/DYP/GAAS HETEROSTRUCTURES/

There is a significant interest in the area of improving high temperat ure stable contacts to III-V semiconductors. Two attractive material s ystems that offer promise in this area are dysprosium phosphide/galliu m arsenide (DyP/GaAs) and dysprosium arsenide/gallium arsenide (DyAs/G aAs). Details of epitaxial growth of DyP/GaAs and DyAs/GaAs by molecul ar beam epitaxy (MBE), and their characterization by x-ray diffraction , transmission electron microscopy, atomic force microscopy, Auger ele ctron spectroscopy, Hall measurements, and high temperature current-vo ltage measurements is reported. DyP is lattice matched to GaAs, with a room temperature mismatch of less than 0.01% and is stable in air wit h no sign of oxidation, even after months of ambient exposure. Both Dy P and DyAs have been grown by solid source MBE using custom designed g roup V thermal cracker cells and group III high temperature effusion c ells. High quality DyP and DyAs epilayer were consistently obtained fo r growth temperatures ranging from 500 to 600 degrees C with growth ra tes between 0.5 and 0.7 mu m/h. DyP epilayers are n-type with electron concentrations of 3 x 10(20) to 4 x 10(20) cm(-3), room temperature m obilities of 250 to 300 cm(2)/V.s, and a barrier height of 0.81 eV to GaAs. DyAs epilayers are also n-type with carrier concentrations of 1 x 10(21) to 2 x 10(21) cm(-3), and mobilities between 25 and 40 cm(2)/ V.s.