AlGaN-based structures on sapphire for visible blind Schottky-barrier UV photodetectors: toward high-performance device applications

Al_xGa_1-xN material system, whose bandgap lies in the 3.42-6.2 eV range, is extremely interesting for visible and solar blind UV photodetector applications. This paper describes the device performances of Al_xGa_1-xN UV Schottky barrier photodetectors for visible-blind applications grown on c-oriented sapphire, with a detailed balance with the basic materials properties. Conventional low temperature grown AlN or GaN were used in all applications. High quality Schottky barrier photodiodes made of Epitaxial Lateral Overgrown (ELOG) GaN are also presented. All Schottky barrier devices show a fast time response, a high UV-visible rejection factor, and high absolute values of above bandgap responsivities. A new application of AlGaN UV Schottky barrier photodetectors to monitor the biological action of the solar UV radiation, as well as the device performance of high quality GaN and AlGaN Metal Semiconductor Metal with cutoff wavelengths as short as 310 nm, are described in detail.