High visible rejection AlGaN photodetectors on Si(111) substrates

We report on the fabrication and characterization of Schottky barrier photo detectors based on Si-doped Al0.35Ga0.65N layers grown on Si(111) substrate s, 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 v isible rejection (> 10(4)) and a responsivity of 5 mA/W at 257 nm are reach ed. The detector time response is limited by the resistancexcapacitance pro duct, with a minimum time constant of 20 ns in the zero-load-resistance lim it. After photodiode voltage breakdown, the effect on the detector response is discussed. (C) 2000 American Institute of Physics. [S0003-6951(00)03319 -2].