Current-voltage, capacitance-voltage and conventional deep level transient spectroscopy at temperature ranges from 40-300 K have been employed to study the influence of alpha-particle irradiation from an 241 Am source on Ni/4H-SiC Schottky contacts. The nickel Schottky barrier diodes were resistively evaporated on n-type 4H-SiC samples of doping density of 7.1 × 10 15 cm −3 . It was observed that radiation damage caused an increase in ideality factors of the samples from 1.04 to 1.07, an increase in Schottky barrier height from 1.25 to 1.31 eV, an increase in series resistance from 48 to 270 Ω but a decrease in saturation current density from 55 to 9 × 10 −12 Am −2 from I-V plots at 300 K. The free carrier concentration of the sample decreased slightly after irradiation. Conventional DLTS showed peaks due to four deep levels for as-grown and five deep levels after irradiation. The Richardson constant, as determined from a modified Richardson plot assuming a Gaussian distribution of barrier heights for the as-grown and irradiated samples were 133 and 151 Acm −2 K −2 , respectively. These values are similar to literature values.

Irradiation experiments have been carried out on 1.9 × 10 16 cm -3 nitrogen-doped 4H-SiC at room temperature using 5.4 MeV alpha-particle irradiation over a fluence ranges from 2.6 × 10 10 to 9.2 × 10 11 cm -2 . Current-voltage (I-V), capacitance-voltage (C-V) and deep level transient spectroscopy (DLTS) measurements have been carried out to study the change in characteristics of the devices and free carrier removal rate due to alpha-particle irradiation,

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.

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We have studied the defects introduced in n-type 4H-SiC during electron beam deposition (EBD) of tungsten by deep-level transient spectroscopy (DLTS). The results from currentvoltage and capacitance-voltage measurements showed deviations from ideality due to damage, but were still well suited to a DLTS study. We compared the electrical properties of six electrically active defects observed in EBD Schottky barrier diodes with those introduced in resistively evaporated material on the same material, as-grown, as well as after high energy electron irradiation (HEEI). We observed that EBD introduced two electrically active defects with energies E C -0.42 and E C -0.70 eV in the 4H-SiC at and near the interface with the tungsten. The defects introduced by EBD had properties similar to defect attributed to the silicon or carbon vacancy, introduced during HEEI of 4H-SiC. EBD was also responsible for the increase in concentration of a defect attributed to nitrogen impurities (E C -0.10) as well as a defect linked to the carbon vacancy (E C -0.67). Annealing at 400 °C in Ar ambient removed these two defects introduced during the EBD.