The effect of high energy electron (HEE) irradiation on nickel Schottky contacts fabricated on lowly doped n-type 4H-SiC was investigated by deep level transient spectroscopy (DLTS) and high resolution Laplace-DLTS. The Schottky contacts were deposited by resistive evaporation of nickel and were observed to be of good rectification quality from current-voltage measurements. DLTS was performed up to 350K to investigate the presence of defects before and after HEE irradiation. HEE irradiation was observed to induce three deep level defects below 350 K at 0.42 eV, 0.62 eV and 0.76 eV below the conduction band minimum. These deep level defects are labelled E-0.42, E-0.67 and E-0.76. Defects E-0.42 and E-0.76 were observed after the same electron fluence and were annealed out at the same temperature, suggesting that the defects could be strongly related. The effect of HEE irradiation and annealing on as-grown defects was also investigated and is reported. (C) 2017 Elsevier B.V. All rights reserved.

Au/Ni (20:80) Schottky barrier diodes (SBDs) were resistively evaporated on nitrogen-doped n-type 4H-SiC. Current-voltage (I-V) and capacitance-voltage (C-V) characteristics of the SDBs were investigated before and after bombardment with 1.8 MeV proton irradiation at a fluence of 2.0 x 10(12) cm(2). The measurements were carried out in the temperature range 40-300 K in steps of 20 K. Results obtained at room temperature (300 K) showed highly rectifying devices before and after bombardment. It was observed that the proton irradiation induced an increase of ideality factor from 1.05 to 1.13, a decrease in Schottky barrier height from 1.40 to 1.22 eV, an increase in series resistance from 10 to 66 n and a noticeable increase of the saturation current from 3.0 x 10(-21) to 6.8 x 10(-1)2A. The increase in saturation current after proton irradiation was attributed to the presence of interfacial states created by irradiation induced defects. Thermionic emission dominated the I-V characteristics in the temperature range 120300 K but the I-V characteristics deviated from thermionic emission theory at temperatures below 120 K for devices both before and after irradiation. The variation of the SBDs characteristics with temperature was attributed to the presence of lateral inhomogeneities of the SBH. Modified Richardson constants were determined from a Gaussian distribution of barrier heights to be 133 and 165 A cm(-2) K-2 before and after irradiation, respectively. (C) 2017 Elsevier B.V. All rights reserved.

We have used deep level transient spectroscopy (DLTS) and Laplace DLTS (L-DLTS) to characterize the electrically active point defects introduced in n-type gallium arsenide by electron beam exposure prior to Schottky metallization. The GaAs crystals were exposed to incident electrons at sub-threshold energies which are deemed low and insufficient to form defects through ion solid interactions. DLTS revealed a set of electron traps different from those commonly observed in n-GaAs after particle irradiation. These different signatures from the same radiation type suggest that different mechanisms are responsible for defect formation in the two electron irradiation processes. An analysis of the conditions under which the defects were formed was done to distil a number of possible defect formation mechanisms using the experimental evidence obtained. (C) 2017 Elsevier B.V. All rights reserved.

We present results of the structural, energetic and electronic properties of rare earth (RE) interstitial complexes in Ge (REGeGei; for RE: Ce, Pr, Eu, Er and Tm). We used the Heyd, Scuseria, and Ernzerhof (HSE06) hybrid functional within the framework of density functional theory for all calculations. The energy of formation and charge state transition levels of REGeGei complexes were obtained. For the neutral charge state, the results of the formation energy of the REGeGei, were between 0.21 and 8.14 eV. Amongst the REGeGei, while the CeGeGe, was energetically the most favourable with a binding energy of 3.90 eV, TmGeGei and ErGeGei were not stable with respect to their binding energies. The CeGeGei induced deep donor level with negative-U ordering, the PrGeGei induced shallow levels close to the valence band maximum and the EuGeGei induced a shallow single donor level. (C) 2017 Elsevier B.V. All rights reserved,

The Heyd, Scuseria, and Ernzerhof (HSE06) hybrid functional by means of density functional theory has been used to model the electronic and structural properties of rare earth (RE) substitutional impurities in germanium (REGe). The formation and charge state transition energies for the REGe (RE = Ce, Pr, Er and Eu) were calculated. The energy of formation for the neutral charge state of the REGe lies between -0.14 and 3.13 eV. The formation energy result shows that the Pr dopant in Ge (Pr-Ge) has the lowest formation energy of -0.14 eV, and is most energetically favourable under equilibrium conditions. The REGe induced charge state transition levels within the band gap of Ge. Shallow acceptor levels were induced by both the Eu (Eu-Ge) and Pr (Pr-Ge) dopants in Ge. The Ce-Ge and Er-Ge exhibited properties of negative-U ordering with effective-U values of -0.85 and -1.07 eV, respectively. (C) 2017 Elsevier B.V. All rights reserved.