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/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.

Progress on AlGaN-based solar-blind ultraviolet photodetectors and focal plane arrays

“…Additionally, AlGaN exhibits a high specific detectivity approximately 10 12 cm Hz 1/2 W −1 33 . Based on these outstanding optoelectronic characteristics, AlGaN ternary alloys exhibit marked advantages in promoting the evolution of UV photodetectors (PDs), particularly in fabricating intrinsic solar-blind UV detectors 34 , 35 .…”

Current advances in solar-blind photodetection technology: using Ga2O3 and AlGaN

“…For instance, AlGaN-based SB four-quadrant Schottky photodiodes were fabricated by depositing Au contacts. 68 The cut-off wavelength for each quadrant was (275) nm, with a responsivity of 28 mA W −1 and quantum efficiency of 14% at 250 nm. In another study, Schottky photodiodes made of indium–silicon co-doped Al x Ga 1− x N with a high mobility and Hall electron concentration of 40 cm 2 V −1 s −1 and 8 × 10 17 cm −3 , respectively, yielded a responsivity of 0.033 A W −1 at 275 nm.…”

High photocurrent gain in NiO thin film/M-doped ZnO nanorods (M=Ag, Cd and Ni) heterojunction based ultraviolet photodiodes

“…Wide bandgap semiconductor based ultraviolet (UV) photodiodes have attracted significant interest compared with UV photodiodes based on narrow bandgap semiconductors due to their high quantum efficiency, enhanced photocurrent gain and large UV/visible rejection ratio [1][2][3][4][5]. Wide bandgap semiconductor nanostructures such as nanorods are promising for the improvement of UV photodiodes since they have a large surface area to volume ratio which leads to high internal photoconductivity gain due to the surface enhanced electron-hole separation efficiency [6,7].…”