Implementation of an AlGaN-based solar-blind UV four-quadrant detector

Abstract

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/cm2, a series resistance of (120±30)Ω and a free carrier concentration of (1.6±0.3)×1018cm−3. Spectral characterization on the photosensitive area of 7.3×10−3cm2 yielded a cut-off wavelength at (275±5)nm (4.59eV to 4.23eV) 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 a quantum efficiency of (14±1)% at 250nm. The ultraviolet-to-visible and near-infrared rejection ratio was between 103 and 105 for most of the quadrants. Characterization showed uniformity across the quadrants, proving the detector feasible for implementation in future ultraviolet-sensitive electro-optic devices.