Schottky-barrier photodiode using p-diamond epilayer grown on p+-diamond substrates

In order to understand a substrate effect on photoresponse properties of diamond-based Schottky-barrier photodiode (SPD), we utilize a heavily boron-doped p(+)-diamond substrate for a thin epilayer growth and the SPD fabrication. Vertical- and planar-types SPD's show excellent rectifying property with ideality factor close to unity and on-resistance as small as 1 Omega.cm(2). Both the SPD's are operable in photovoltaic and reverse bias modes with a quantum efficiency of 2.2 +/- 0.5% and does not provide a photoconductivity gain and a persistent photocurrent before and after annealing at 500 degrees C for 120 min. By comparing the photoresponse properties of SPD's on the p(+)-diamond substrate with on a Ib-diamond substrate, we conclude that a homojunction between p-diamond epilayer and Ib-diamond substrate governs a photo-carriers generation and a transport process, which produces an excellent spectral response property of SPD on the Ib-diamond substrate. (C) 2008 Elsevier B.V. All rights reserved.