This study reports on the effect of resistive physical vapour deposition of Pd Schottky contacts on the defects observed in an irradiated n-type Si substrate. Deep-level transient spectroscopy (DLTS) was used in order to investigate the possible defects in Schottky diodes on the n-type Si. In this study the defects present where the diode was deposited first and then irradiated (“post irradiated”) were compared to those present where the substrate was irradiated first, and the Pd deposited after irradiation (“pre-irradiated”). In the post-irradiated material, the familiar radiation-induced defects were observed. However, in the pre-irradiated material, fourteen new defects were observed, with DLTS signatures differing from those of the defects in the post-irradiated diodes. The newly identified defects seemed to be specifically caused by the deposition of Pd contacts after irradiation of the substrate, as these defects were not observed when other metals such as Au, Ni, Al and Ag were deposited after irradiation. In this paper, we will refer to the observed effect that Pd deposition replaced the familiar radiation-induced defects in Si with the new set of defects as the “Pd effect”. Careful experiments ruled out annealing due to inadvertent heating of the sample during deposition as a possible cause. Care was taken to avoid all sources of contamination: The effect was observed for different sources of Pd and crucibles. This effect was inhibited by the presence of a thin intermediate layer of Pd or Au deposited before irradiation. We therefore conclude that the effect is only observed when Pd is deposited directly onto the irradiated Si surface. Out of the fourteen newly observed defects, four defects, with activation energy of 182, 220, 360 and 607 meV, had DLTS signatures corresponding to those of defects previously observed in Pt-containing Si. For the rest of the defects, no defects with similar DLTS signatures were found in literature. We therefore believe that the defects observed are produced by defect enhanced diffusion of Pd. Overall, the study enhances our understanding of defect behaviour in silicon-based devices, particularly under irradiation and metal deposition conditions, and reveals the unique properties and effects of Pd.

4H-SiC Schottky barrier diodes (SBDs) were exposed to 5.4 MeV alpha particles with fluences of 2.55× 1011 cm−2, 5.11 × 1011 cm−2 and 7.67 × 1011 cm−2, respectively. Transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) was used to determine the structure and cross-sectional elemental composition of the device, while current–voltage and capacitance–voltage profiling were used to determine the primary electrical device-characteristics before and after irradiation. EDS revealed the presence of a <1 μm Ti layer, covered by 5 μm Al layer, in intimate contact with the SiC. Deep level transient spectroscopy (DLTS), performed in the temperature range 15–310 K, revealed one dominant peak around 50 K (Ec - 0.07 eV) in the unirradiated samples. This peak showed asymmetry suggesting that it may consist of more than one defect. Notably, Z1/2, the carbon vacancy-related (Vc) defect commonly observed in as-grown n-type 4H-SiC, was not detected in the unirradiated reference sample. After irradiation, a broad peak emerged around 280 K (at 80 Hz), most likely Z1/2, having a shoulder around 180 K, was detected. Increasing the fluence resulted in a corresponding decrease in the concentration of the electron trap observed around 50 K (Ec - 0.07 eV), while the concentration increases for the defect detected around 280 K. Notably, the concentration of Z1/2 was found to be strongly fluence dependent and linked to what we believe is a related to a silicon vacancy transition, labelled S1/2 in literature. Laplace DLTS confirmed that the peak observed around 50 K is composed of multiple defects.

The RF sputter deposition was used to fabricate Au Schottky barrier diodes on Si-doped n-type GaAs with two different carrier densities (1 x 10(15) cm(-3), 1 x 10(16) cm(-3) and partially 8 x 10(16) cm(-3)) at a power of 150 W. Deep-level transient spectroscopy (DLTS) and Laplace DLTS were used to measure the electrical properties of the sputter-induced defects near the surface of the GaAs. By using DLTS, we found that the samples contained six defects (S1 (0.046 eV), S2 (0.22 eV), S3 (0.30 eV), S4 (0.55 eV), S5 (0.56 eV) and S6 of which three (S1, S3 and S5) were metastable and one (S4) was highly dopant concentration dependent. S6 was observed close to where the EL2 was expected, but had different properties and two components which could be resolved by Laplace DLTS: S6a (0.83 eV) and S6b (0.84 eV). The depth profile showed a difference in depth distribution of the defects in the samples which shows by increasing depth, a rapid decay of defect concentration. The electric field dependence of the S3 defect could be explained by a combination of Poole-Frenkel and phonon-assisted tunnelling mechanisms while for the S4 and S5 defects the emission of carriers indicate the phonon-assisted tunnelling. True capture cross-section measurements were done, and the S3 defect had a much lower capture cross-section than the S4 and S5 defects and the real capture cross-section of S3 and S4 defects is in the range of Auger mechanism while for the S5 defect indicates multiphonon emission. Finally, measurements as to the effect of annealing on I-V characteristics were carried out on the sputtered samples as well.

In this study, nitrogen-doped 4H-SiC samples were bombarded with 167 MeV xenon ions to a fluence of 1 × 108 cm−2 at 300 K prior to the fabrication of Schottky barrier diodes. The implanted samples were annealed at approximately 900 °C for 1 h before the resistive evaporation of nickel Schottky barrier diodes. In comparing the current–voltage results of the implanted devices with as-deposited ones, generation-recombination took place in the implanted Schottky barrier diodes. Four defects (100, 120, 170, and 650 meV) were present in as-deposited Schottky barrier diodes when characterized by deep level transient spectroscopy (DLTS). In addition to the defects observed in the as-deposited samples, two additional defects with activation energies of 400 and 700 meV below the conduction band minimum were induced by Xe ions implantation. The two deep level defects present have signatures similar to defects present after irradiated by MeV electron. The two defects present after irradiation disappeared after annealing at 400 °C which indicate instability of the defects after annealing implanted samples.

The capture barrier energy of the E-center deep level defect introduced in Pd/Sb-doped Ge by alpha-particle irradiation has been studied. Palladium Schottky barrier diodes (SBDs) fabricated by resistive evaporation technique were successfully characterised by current-voltage (I-V), capacitance-voltage (C-V), conventional and Laplace deep level transient spectroscopy. The rectification quality of Schottky contacts before and after irradiation was confirmed by I-V and C-V results. The ideality factor and doping density were determined to be in the range of 1.23 to 1.46 and 3.55 x 10(15) to 5.25 x 10(15) cm(-3), respectively before and after irradiating the device with alpha-particles. The thermal emission activation energy and the apparent capture cross section of the E-center were determined from the Arrhenius plot to be 0.37 eV and 1.3 x 10(-15) cm(2), respectively. The capture barrier energy and the true capture cross section of the E-center were calculated to be 0.052 eV and 2.25 x 10(-17) cm(2), respectively from the experimental findings after varying the pulse width at different temperature range from 145 to 180 K in steps of 5 K.

Deep-level transient spectroscopy measurements on β-Ga2O3 crystals reveal the presence of three defect signatures labeled E2a, E2b, and E3 with activation energies at around 0.66 eV, 0.73 eV, and 0.95 eV below the conduction band edge. Using secondary ion mass spectrometry, a correlation between the defect concentration associated with E3 and the Ti concentration present in the samples was found. Particularly, it is found that E3 is the dominant Ti-related defect in β-Ga2O3 and is associated with a single Ti atom. This finding is further corroborated by hybrid functional calculations that predict Ti substituting on an octahedral Ga site, denoted as TiGaII, to be a good candidate for E3. Moreover, the deep level transient spectroscopy results show that the level previously labeled E2 and attributed to Fe substituting on a gallium site (FeGa) consists of two overlapping signatures labeled E2a and E2b. We tentatively assign E2a and E2b to Fe substituting for Ga on a tetrahedral or an octahedral site, respectively.

Barrier height inhomogeneities on Pd/n-type 4H-SiC Schottky barrier diodes in the 300-800 K temperature range have been investigated. Palladium is known to form silicide above 673 K. Temperature dependent current-voltage (I-V) characteristics were analyzed. Barrier height (BH) and ideality factor (n) were found to be strongly temperature dependent. Barrier height increased, whilst ideality factor decreased with increasing in temperature and the Richardson plot showed some deviation from linearity. This was attributed to barrier inhomogeneities at the metal-semiconductor interface which resulted in a distribution of barrier heights. From the modified Richardson plot, the modified Richardson constant, A** was found to be 155 Acm(-2)K(-2) and 87 Acm(-2)K(-2) in the 300-525 K and the 550-800 K temperature ranges respectively.

This work presents the effect of electron irradiation on the full symmetric cell using the pure polymer base AC material and irradiation on the full cell was analyzed for different exposure times. An improvement of the current response and ideal EDLC behaviour of the full device was also recorded with increased exposure to electron irradiation for up to 48 h. However, after the source of irradiation was removed, the original capacitance of the device was restored. This interesting phenomenon is a novel finding which is being reported for the first time. The recovery of the material after the radiation source terminated is based on the ability of the carbon-based nanostructured material to self-heal itself in a bid to return to its original form. These results suggest that radiation can improve supercapacitor performance permanently or temporary based on the radiation source.

Primary defects introduced in boron-doped silicon by an alpha-particle source with a fluence rate of 7 x 10(6) cm(-2) s(-1) at cryogenic temperatures were investigated using deep-level transient spectroscopy (DLTS). The data showed that the defects observed between 35 K and 120 K were not detectable when irradiation was carried out at room temperature. The defect levels were observed at 0.10 eV, 0.14 eV and 0.18 eV above the valence band maximum. These levels were attributed to the boron-substitutional vacancy complex, the mono vacancy and a vacancy-related defect respectively.

Au Schottky barrier contacts (SBDs) were DC sputter deposited on Si doped n-type GaAs at a power of 150 W. Deep-level transient spectroscopy (DLTS) and Laplace DLTS were used to characterize the sputter-induced defects near the surface of the GaAs. In this study, I-V and C-V measurements showed that the sputter deposited diodes had a significantly lower barrier height and a higher free carrier density. Using DLTS, it was found that this sample contained seven defects - three of them were metastable while one of the others was highly dopant dependent. The energy levels of these defects are E-c - 0.046 eV, E-c - 0.22 eV, E-c - 0.30 eV, E-c - 0.55 eV, E-c - 0.56 eV, E-c - 0.83 eV and E-c - 0.84 eV. The EL2 defect was not observed in the sputtered samples, but one of the sputter-induced defects emitted in the same range as the EL2, however, it had two components and their DLTS signatures (E-c - 0.83 eV and E-c - 0.84 eV) differed significantly from that of the EL2. By applying different bias conditions ( - 2 V and zero V) for annealing procedures, the metastable defects (E-c - 0.30 eV and E-c - 0.56 eV) were transformed into each other. The pre-factor obtained from transformation rate of E-c - 0.56 eV -> E-c - 0.30 eV under reverse bias was 3 x 10(15) s(-1) which is related to free carrier emission.

Ni/4H-SiC Schottky barrier diodes have been irradiated by 5.4-MeV helium ions at cryogenic temperatures and their electrical characteristics investigated. Only the prominent native defects (E-0.11, E-0.16, and E-0.65) were observed before and after low-temperature irradiation at 50K, with a baseline on the spectrum observed starting at 190K. Low-temperature irradiation reduced the concentration of native E-0.11 and E-0.16 defects. After annealing at 380K, E-0.37, E-0.58, E-0.62, E-0.73, and E-0.92 defects were observed. These results show that E-0.62, an acceptor level of the Z(1) center, and E-0.73, an acceptor level of the Z(2) center, are both secondary defects which are not formed directly from the irradiation process but from succeeding thermal reactions. An interpretation of the formation of the secondary defects is given.

We have used confocal Raman spectroscopy, atomic force microscopy (AFM), Binary collision approximations and Deep level transient spectroscopy (DLTS) to study the defects introduced in n-type 4H-SiC by 167 MeV Xe26+ ions (swift heavy ions (SHIs)). Moderately doped epitaxial layers were irradiated with SHIs to a fluence of 5 x 10(11) cm(-2) at room temperature. Raman spectroscopy was used to investigate the effects of irradiation on the crystal structure. Raman intensity reduced after irradiation but the overall bond structure was conserved. Cluster spectra from confocal Raman spectroscopy showed a damage impact that was consistent with SRIM simulations. AFM showed that the incident radiation resulted in elongated protrusions. The virgin samples contained the E-0.09, E-0.12, E-0.15 and E-0.65 as the only electrically active defects. After irradiation the E-0.40 and E-0.71 defects were introduced.

ZnO thin films were prepared using the sol-gel spin coating technique. The structure was investigated using X-ray diffraction (XRD). The XRD spectra exhibited typical randomly orientated structure with a slight preference for growth along the (002) plane and a crystallite size of similar to 48 nm. The Schottky barrier diodes were fabricated on the synthesized ZnO thin films. The electrical properties before and after irradiating the devices with alpha particle irradiation were characterized using current-voltage (I-V), capacitance-voltage (C-V), deep-level transient spectroscopy (DLTS) and Laplace-transform deep-level transient spectroscopy (L-DLTS) techniques. Pd/ZnO/n-Si/AuSb Schottky diodes exhibited good rectifying properties. Before irradiation, the DLTS spectra revealed one defect E-4 with activation enthalpy 0.41 eV. After irradiation, there is a new defect E-alpha with the activation enthalpy 0.35 eV. Laplace-transform deep-level transient spectroscopy (L-DLTS) revealed the fine structure of the E-alpha to be made up of 0.53 eV and 0.36 eV defects.

In this paper, we report on defects introduced in epitaxially grown n-type silicon (Si) during electron beam exposure. The defects observed were electrically characterized using deep-level transient spectroscopy (DLTS) and high-resolution Laplace DLTS. In this process, Si samples were first exposed to the conditions of electron beam deposition (EBD) without depositing a metal. In this paper, this process is called electron beam exposure (EBE). After 50 minutes of EBE, gold Schottky contacts were fabricated using a resistive deposition method. The defect levels E(0.11) and E(0.17) seem to be associated with the carbon interstitial-substitutional pair CiCs. The CiCs-defect is a bistable defect with an amphoteric character in two defect configurations: A and B. The transition from configuration A to B and vice versa is made possible by a simple bond-switching transformation. A defect level E(0.21) was observed, but the defect's structure is not clear. E(0.41) and E(0.45) were also observed, associated with a divacancy and a phosphorous interstitial, respectively. E(0.47) and E(x) were observed, but their structures are still a subject of speculation.

In this paper we used high-resolution Laplace deep-level transient spectroscopy (DLTS) to study the electrical properties of the E3 defect family introduced in GaAs by MeV electron irradiation. We found that the peak conventionally referred to as the E3 contained 3 components which we labeled E3a, E3b and E3c, with E3a being the most prominent component. The activation energy of E3a for different carrier densities varied between 0.36 and 0.375 eV. From dopant dependent introduction rate measurements, we found that the introduction rates of the E3a and E3b defect did not depend on doping density. However, the E3c concentration increased with increasing carrier density. Furthermore, the E3c was found to be metastable: it was reversibly removed during minority carrier injection at low temperatures and re-introduced by annealing above 160 K under zero bias. Interestingly, annealing measurements revealed that, of the three components, the E3b annealed first at around 500 K while both the other components annealed together at a higher temperature of 525 K. By comparing our results with previous studies, we concluded that the origin of E3a is V-As, E3b is As-i and E3c is V-Ga-Si-Ga.

We have studied the defects introduced in n-type 4H-SiC during sputter deposition of tungsten using deep-level transient spectroscopy (DLTS). Current-voltage and capacitance-voltage measurements showed a deterioration of diode thermionic emission characteristics due to the sputter deposition. Two electrically active defects E-0.29 and E-0.69 were introduced. Depth profiling revealed that sputter deposition increases the concentration of the native Z(1) defect. A comparison with prominent irradiation and process induced defects showed that the E-0.29 was unique and introduced during sputter deposition only. The E-0.69 may be silicon vacancy related defect.

Deep level transient spectroscopy was used to study the defects induced by alpha-particle irradiation from an Am241 source in antimony doped n-type germanium. Previous investigations of the well know Sb-vacancy defect have led to the discovery of a second defect with very similar emission properties, referred to as the E′. Although both defects have similar emission rates, they have very different annealing properties. In this study we further investigated these properties of the E′ in Sb doped samples irradiated at 270K with alpha particles from an Am241 source. Laplace deep level transient spectroscopy was used to determine the concentration of each defect. An isothermal annealing study of the E′ was carried out in the temperature range 300K to 325K in 5K increments, while the Sb-vacancy was annealed out completely at 410K onwards, long after the E′ was completely annealed out. The annealing activation energy was determined through isothermal annealing profiles for both the Sb-Vacancy and the E′ as 1.05eV and 0.73eV respectively with a prefactor of 2.05 × 109s−1 and 2.7 × 108s−1.

The effects of isochronal annealing on the electrical, morphological and structural characteristics of Au/Ni/4H-SiC Schottky barrier diodes (SBDs) have been studied. Current–voltage (I–V), capacitance–voltage (C–V), deep-level transient spectroscopy, scanning electron microscope (SEM) and X-ray diffraction measurements were employed to study the thermal effect on the characteristics of the SBDs. Prior to thermal annealing of Schottky contacts, the I–V measurements results confirmed the good rectification behaviour with ideality factor of 1.06, Schottky barrier height of 1.20 eV and series resistance of 7 Ω. The rectification properties after annealing was maintained up to an annealing temperature of 500 °C, but deviated slightly above 500 °C. The uncompensated ionized donor concentration decreased with annealing temperature, which could be attributed to out-diffusion of the 4H-SiC into the Au/Ni contacts and decrease in bonding due to formation of nickel silicides. We observed the presence of four deep-level defects with energies 0.09, 0.11, 0.16 and 0.65 eV below the conduction band before and after the isochronal annealing up to 600 °C. The conclusion drawn was that annealing did not affect the number of deep-level defects present in Au/Ni/4H-SiC contacts. The variations in electrical properties of the devices were attributed to the phase transformations and interfacial reactions that occurred after isochronal annealing.

We have characterised the deep level defects present before and after annealing the proton-irradiated Ni/nitrogen-doped 4H-SiC Schottky barrier diodes (SBDs) using deep level transient spectroscopy. The bombardment of the sample was carried out at a fluence of 1.0 x 10(12) cm(-2). The quality of the Ni/4H-SiC SBDs was evaluated before and after proton irradiation and annealing by current-voltage (I-V) and capacitance-voltage (C-V) measurements, carried out at room temperature (300 K). The I-V and C-V results revealed extensive degradation of the diodes properties after proton irradiation at the aforementioned fluence. Rectification properties of the Ni/4H-SiC SBDs recovered gradually after annealing in flowing argon at temperatures varying from 125 to 625 degrees C. The presence of four electron traps (E-c - 0.10, E-c - 0.13, E-c - 0.18 and E-c - 0.69 eV) was observed in as-grown Ni/4H-SiC SBDs. Deep level defects, E-c - 0.42 and E-c - 0.76 eV, were revealed after annealing the proton-irradiated SBDs up to 225 degrees C. The two defects observed at 225 degrees C later annealed out at 425 degrees C, causing a significant change in the spectrum. The annealing out of E-c - 0.42 and E-c - 0.76 eV at 425 degrees C was concurrent with detection of two electron traps, E-c - 0.31 and E-c - 0.62 eV. We speculate that the defects E-c - 0.42 and E-c - 0.76 eV have a link or relationship with defects E-c - 0.31 and E-c - 0.62 eV, respectively. The defect, E-c - 0.31 eV, was stable up to high temperature annealing and was attributed to a carbon interstitial.