New photoluminescence lines in Vanadium doped GaAs grown by MOVPE
We examined the electrical and optical properties of vanadium-doped GaAs grown by metalorganic vapour phase epitaxy using vanadium tetrachloride (VCl4) as a novel dopant source. Samples with various vanadium incorporations were investigated. All samples were n type. The electron concentration dependence on the VCl4 flow rate was established. At 15 K, by comparison with undoped layers grown in the same conditions, photoluminescence spectra of V-doped exhibited three new emission bands: at 1.41, 1 and 0.72 eV. The 1 and 0.72 eV band emissions were attributed to V 2þ and V 3þ intracenter emission, while the 1.41 eV band was suggested to be a donor-bound transition. The identity of the donor is tentatively attributed to a donor complex that associates vanadium to an arsenic vacancy. From Hall effect as function of temperature, the donor ionisation energy was estimated to be about 102 ^ 5 meV. q 2003 Elsevier Science Ltd. All rights reserved.
Evidence for complexes of hydrogen with deep-level defects in bulk III-V materials.
Etude spectroscopique montrant la presence d'hydrogene dans des composes III-V non dopes a l'hydrogene. Formation de complexes entre l'hydrogene et des impuretes metalliques ou d'autres defauts
Composite monolayer fabrication by an arc-spray process
A single layer (monotape) technique for fabricating complex high-temperature tungsten-fiber-reinforced superalloy composites is proposed. The fabrication of sheets of arc-sprayed monotape 38 cm wide and 122 cm long has been demonstrated. Composites fabricated using the method are shown to have equal tensile strength and a cleaner matrix than composites fabricated from powder metal cloth monotapes, and the present technique is less expensive than the powder metal fabrication techniques.