An AlGaN-based front illuminated intrinsically solar-blind ultraviolet four-quadrant Schottky detector was fabricated and characterized. A layered ohmic structure was deposited followed by a multi-step annealing method. Ultraviolet transmissive iridium oxide was used as the Schottky barrier material and formed by a two-step annealing method. Au contacts were deposited on the Schottky contacts and annealed. The detector was mounted onto a commercial chip carrier and wires were epoxy bonded from the ohmic and Au contacts to the carrier strips. The detector had an average ideality factor of 1.97 ± 0.08, a Schottky barrier height of (1.22 ± 0.07) eV, a reverse leakage current density of (2.1 ± 4) nA/cm 2 , a series resistance of (120 ± 30) Ω and a free carrier concentration of (1.6 ± 0.3) × 10 18 cm −3 . Spectral characterization on the photosensitive area of 7.3 × 10 −3 cm 2 yielded a cut-off wavelength at (275 ± 5) nm (4.59 eV to 4.23 eV) for each quadrant, corresponding to the absorption edge of a (46 ± 3)% Al content AlGaN-based material. The detector had an average responsivity of (28 ± 2) mA/W and quantum efficiency of (14 ± 1)% at 250 nm. The ultraviolet-to-visible and near-infrared rejection ratio was between 10 3 and 10 5 for most of the quadrants. Characterization showed uniformity across the quadrants, proving the detector feasible for implementation in future ultraviolet-sensitive electro-optic devices.
The effects of ZnO annealing have for the first time been investigated on the rectification behaviour of highly rectifying Pd Schottky contacts deposited on ZnO using the current-voltage (IV) and capacitance-voltage (CV) measurement techniques. IV results reveal a decrease in the contact quality with increasing annealing temperature as confirmed by a decrease in the zero bias barrier height and an increase in the reverse current measured at -1.5 V. An average barrier height of (0.77 ± 0.02) eV has been calculated by assuming pure thermionic emission for the as-
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