%0 Journal Article
%T Zinc Selenide-Based Schottky Barrier Detectors for Ultraviolet-A and Ultraviolet-B Detection
%A V. Naval
%A C. Smith
%A V. Ryzhikov
%A S. Naydenov
%A F. Alves
%A G. Karunasiri
%J Advances in OptoElectronics
%D 2010
%I Hindawi Publishing Corporation
%R 10.1155/2010/619571
%X Wide-bandgap semiconductors such as zinc selenide (ZnSe) have become popular for ultraviolet (UV) photodetectors due to their broad UV spectral response. Schottky barrier detectors made of ZnSe in particular have been shown to have both low dark current and high responsivity. This paper presents the results of electrical and optical characterization of UV sensors based on ZnSe/Ni Schottky diodes fabricated using single-crystal ZnSe substrate with integrated UV-A (320每400ˋnm) and UV-B (280每320ˋnm) filters. For comparison, characteristics characterization of an unfiltered detector is also included. The measured photoresponse showed good discrimination between the two spectral bands. The measured responsivities of the UV-A and UV-B detectors were 50ˋmA/W and 10ˋmA/W, respectively. A detector without a UV filter showed a maximum responsivity of about 110ˋmA/W at 375ˋnm wavelength. The speed of the unfiltered detector was found to be about 300ˋkHz primarily limited by the RC time constant determined largely by the detector area. 1. Introduction Schottky barrier photodetectors using wide-bandgap semiconductors have been fabricated for detection of ultraviolet radiation [1每19]. The materials used include SiC [7], III每V nitrides [8, 9], and II每VI compounds such as ZnSe [10每19]. Previous studies by Bouhdada et al. showed that the wide-bandgap ZnSe has a promising spectral response on detection of short wavelengths [15]. Though other wide-bandgap semiconductor materials are readily available, ZnSe has advantages due to its broader wavelength response in the UV spectral range compared to the nitrides [15]. The responsivity of ZnSe detectors was measured to be in the 0.1 A/W range while detectivity as high as ˋcm (Hz)1/2/W was reported [13, 15]. In addition, most wide-bandgap III每V compounds suffer from the lack of lattice-matched substrates on which to grow them while ZnSe is closely lattice matched to GaAs substrates, and high crystalline quality can thus be obtained [20]. ZnSe Schottky diodes have been shown to have a relatively low leakage current which translates into a higher signal-to-noise ratio [17]. The response of ZnSe Shottky detectors was also analyzed to determine various decay mechanisms after light excitation [14]. In this paper, fabrication and characterization of ZnSe/Ni Schottky barrier photodetectors operating in the UV-A and UV-B spectral ranges are described. The detectors were fabricated on 1ˋmm thick n-type (aluminum doped) single crystal ZnSe substrate. 2. Device Fabrication The structure of the ZnSe/Ni Schottky diode sensor is shown
%U http://www.hindawi.com/journals/aoe/2010/619571/