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Browsing by Author "Rodrigues, A. M."

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  • Electrical characterization of CVD diamond-n(+) silicon junctions
    Publication . Rodrigues, A. M.; Gomes, Henrique L.; Stallinga, Peter; Pereira, L.; Pereira, E.
    The electrical characteristics of CVD-diamond/n(+)-Si heterojunction devices are reported. Below 250 K the diodes show an unusual inversion of their rectification properties. This behavior is attributed to an enhanced tunneling component due to interface states, which change their occupation with the applied bias. The temperature dependence of the loss tangent shows two relaxation processes with different activation energies. These processes are likely related with two parallel charge transport mechanisms, one through the diamond grain, and the other through the grain boundary. (C) 2001 Elsevier Science B.V. Ah rights reserved.
    2001Journal article Restricted access Show more
  • Interface properties and capacitance-voltage behaviour of diamond devices prepared by microwave-assisted CVD
    Publication . Rodrigues, A. M.; Gomes, Henrique L.; Rees, J. A.; Pereira, L.; Pereira, E.
    Free standing diamond films were used to study the effect of diamond surface morphology and microstructure on the electrical properties of Schottky barrier diodes. By using free standing films both the rough top diamond surface and the very smooth bottom surface are available for post-metal deposition. Rectifying electrical contacts were then established either with the smooth or the rough surface. The estimate of doping density from the capacitance-voltage plots shows that the smooth surface has a lower doping density when compared with the top layers of the same film. The results also show that surface roughness does not contribute significantly to the frequency dispersion of the small signal capacitance. The electrical properties of an abrupt asymmetric n(+)(silicon)-p(diamond) junction have also been measured. The I-V curves exhibit at low temperatures a plateau near zero bias, and show inversion of rectification. Capacitance-voltage characteristics show a capacitance minimum with forward bias, which is dependent on the environment conditions. It is proposed that this anomalous effect arises from high level injection of minority carriers into the bulk.
    1999Journal article Restricted access Show more
  • Polycrystalline diamond thin film as wide bandgap material: the optoelectronic behaviour and the relationship with the structure
    Publication . Pereira, L.; Pereira, E.; Rodrigues, A. M.; Gomes, Henrique L.
    In this work metal - Microwave Plasma CVD diamond Schottky devices were studied. The current density vs. applied voltage reveals rectification ratios up to 10(4) at \ +/- 2V \. Under illumination an inversion and increase of the rectification is observed. The carrier density is 10(15) cm(-3) and the ideality factors near 1.5. The dark current vs. temperature shows that below 150 K the bulk transport is controlled by a hopping process with a density of defects of 10(16) cm(-3). For higher temperatures an extrinsic ionisation with activation energy of 0.3 eV takes place. The correlation with the polycrystalline nature of the samples is focused.
    2000Conference object Restricted access Show more