High visible rejection AlGaN photodetectors on Si(111) substrates

We report on the fabrication and characterization of Schottky barrier photodetectors based on Si-doped Al0.35Ga0.65N layers grown on Si(111) substrates, for solar UV-band monitoring (lambda < 320 nm). The epilayers have been obtained by plasma-assisted molecular-beam epitaxy, showing a full width at half maximum of 15 arcmin in x-ray diffraction measurements. A very high visible rejection (> 10(4)) and a responsivity of 5 mA/W at 257 nm are reached. The detector time response is limited by the resistancexcapacitance product, with a minimum time constant of 20 ns in the zero-load-resistance limit. After photodiode voltage breakdown, the effect on the detector response is discussed. (C) 2000 American Institute of Physics. [S0003-6951(00)03319-2].