METALORGANIC VAPOR-PHASE EPITAXY-GROWN ALGAN MATERIALS FOR VISIBLE-BLIND ULTRAVIOLET PHOTODETECTOR APPLICATIONS

Low-pressure metalorganic vapor-phase epitaxy growth conditions of AlxGa1−xN epilayers on c-oriented sapphire have been optimized for aluminum mole fractions x lying in the 0–0.35 range both on GaN and AlN nucleation layers, with a view to application in visible blind UV photodetectors. Good structural, electrical, and optical properties were obtained for undoped and n-type doped AlGaN alloys on (0001)-oriented sapphire substrates. A typical full width at half maximum of 670–800 arc s is measured for the (0002) x-ray double-diffraction peak in the ω mode of 1-μm-thick AlGaN epilayers grown on a GaN nucleation layer. Room-temperature electron mobilities up to 90 cm2/V s are measured on n-type (1018 cm−3) AlGaN epilayers. The low-temperature photoluminescence (T=9 K) performed on nonintentionally doped AlGaN epilayers with low-Al content (10% and 14%) exhibits reproducibly a sharp exciton-related peak, associated with two phonon replica and does not exhibit any low-photon energy transitions. Optical transmi...

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