Photoresponsivity of ultraviolet detectors based on InxAlyGa1−x−yN quaternary alloys

Abstract

We describe the growth, fabrication, and characterization of an ultraviolet (UV) photoconductive detector based on InxAlyGa1−x−yN quaternary alloy that is lattice matched to GaN. The detector consisted of 0.1 μm InxAlyGa1−x−yN alloy grown on 0.5–1.0 μm GaN epilayer by metalorganic chemical vapor deposition. With varying indium concentration, the cut-off wavelength of the InxAlyGa1−x−yN detectors could be varied to the deep UV range. The most important and intriguing result is that the responsivity of the InxAlyGa1−x−yN quaternary alloy exceeded that of AlGaN alloy of a comparable cutoff wavelength by a factor of five. This makes the nitride quaternary alloy very important material for solar blind UV detectors applications particularly in the deep UV range where Al rich AlGaN alloys have problems with low quantum efficiency and cracks due in part to lattice mismatch with GaN. The advantages of InxAlyGa1−x−yN quaternary over AlGaN ternary alloys for UV detector applications are also discussed.