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Planar geometry Schottky barrier photodiodes designed for visible-blind ultraviolet detection have been fabricated. They are based on ZnMgBeSe alloys grown by molecular-beam epitaxy. High crystalline quality is achieved, which leads to a high responsivity (0.17 A/W at 375 nm) and a sharp cutoff of more than three orders of magnitude. As attested by the linear variation of the photocurrent with the optical excitation, there is no internal gain mechanism. A detectivity of 2x10[sup 10] mHz[sup 1/2] W[sup -1] is obtained showing that low-noise devices with high sensitivity have been fabricated. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We report on the characterization of ZnSe- and ZnMgBeSe-based Schottky barrier photodetectors grown on semi-insulating GaAs(001) by molecular-beam epitaxy. The spectral response of the devices shows a very sharp cutoff at variable wavelength, determined by the alloy composition, with a large stop-band rejection. Short-wavelength responsivities of 0.10 A/W and detectivities as high as 1.4x10[sup 12] cm Hz[sup 1/2] W[sup -1] at -3.5 V bias have been achieved. Their time response behavior has been analyzed in detail. When light is switched off, the devices show photocurrent decays in the microsecond range, consisting of two exponential components with very different time constants. The slower component becomes dominant for high load and reverse bias. This behavior is related to the strong frequency dependence of the device capacitance. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]