LOW-PRESSURE CHEMICAL-VAPOR-DEPOSITION OF GAN EPITAXIAL-FILMS

GaN films were grown epitaxially on sapphire and 6H-SiC substrates by low-pressure chemical vapor deposition (LPCVD) using gallium(III) chlo ride and ammonia as gallium and nitrogen precursor, respectively. The properties of these samples were examined by X-ray diffraction. Hall e ffect measurements, secondary-ion mass spectroscopy (SIMS) and photolu minescence (PL). All GaN layers exhibit high free carrier concentratio ns between n = 2 x 10(18) and 5 x 10(19) cm(-3) caused by unintentiona l n-type doping. We provide evidence that this high unintentionally do ping is linked to the oxygen content in the films. The correlation bet ween the optical properties with respect to position and line shape of the band-edge luminescence and the electrical properties, i.e. the fr ee carrier concentration, is discussed. (C) 1998 Elsevier Science B.V. All rights reserved.