Characterisation of defects in electron irradiated Ga-or B-doped CZ Silicon using Laplace DLTS

We have measured the electrical and annealing properties of defects created in Czochralski grown Si doped with either B or Ga by electron irradiation using both conventional and Laplace(L)-DLTS. With L-DLTS, we have been able to resolve several defects that cannot be resolved using conventional DLTS. L-DLTS provides a new avenue to study defect introduction rates and annealing kinetics in B- and Ga-doped Si. The isochronal annealing behaviour of the defects was also investigated

Long range annealing of defects in germanium by low energy plasma ions

Ions arriving at a semiconductor surface with very low energy (2 - 8 eV) are interacting with defects deep inside the semiconductor. Several different defects were removed or modified in Sb-doped germanium, of which the E–center has the highest concentration. The low fluence and low energy of the plasma ions implies that the energy has to be able to travel in a localized way to be able to interact with defects up to a few microns below the semiconductor surface. After eliminating other possibilities (electric field, light, heat) we now conclude that moving intrinsic localized modes (ILMs), as a mechanism of longdistance energy transport, are the most likely cause. This would be striking evidence of the importance of ILMs in crystals and opens the way to further experiments to probe ILM properties both in semiconductors and in the metals used for contacts. Although most of the measurements have been performed on germanium, similar effects have been found in silicon.MICINNSouth African National Research FoundationEuropean Regional Development Fund, Centre of Excellence Mesosystems: Theory and Application

Transport characteristics of Pd Schottky barrier diodes on epitaxial n-GaSb as determined from temperature dependent current-voltage measurements

Please read abstract in the article.SA Research Chairs Initiative of the Department of Science and Technology, National Research Foundation and the NMMU.http://www.elsevier.com/locate/tsfhb201

Interface behaviour and electrical performance of ruthenium Schottky contact on 4H-SiC after argon annealing

Rutherford backscattering spectrometry(RBS) analysis , carried out at various annealing temperatures, of a thin film of ruthenium on n-type 4-hexagonal silicon carbide (4H-SiC) showed evidence of ruthenium oxidation, ruthenium silicide formation and diffusion of ruthenium into silicon carbide starting from an annealing temperature of 400oC. Ruthenium oxidation was more pronounced, and ruthenium and Silicon inter-diffusion was very deep after annealing at 800oC. Raman analysis of some samples also showed ruthenium silicide formation and oxidation. The Schottky barrier diodes showed very good linear capacitance-voltage characteristics and excellent forward current-voltage characteristics, despite the occurrence of the chemical reactions and inter-diffusion of ruthenium and silicon at ruthenium-silicon-carbide interface, up to an annealing temperature of 800oC.http://link.springer.com/journal/12034hb201

Long range annealing of defects in germanium by low energy plasma ions

Ions arriving at a semiconductor surface with very low energy (2–8 eV) are interacting with defects deep inside the semiconductor. Several different defects were removed or modified in Sb-doped germanium, of which the EE-center has the highest concentration. The low fluence and low energy of the plasma ions imply that the energy has to be able to travel in a localized way to be able to interact with defects up to a few microns below the semiconductor surface. After eliminating other possibilities (electric field, light, heat) we now conclude that moving intrinsic localized modes (ILMs), as a mechanism of long-distance energy transport, are the most likely cause. This would be striking evidence of the importance of ILMs in crystals and opens the way to further experiments to probe ILM properties both in semiconductors and in the metals used for contacts. Although most of the measurements have been performed on germanium, similar effects have been found in silicon.MICINN, project FIS2008-04848; the South African National Research Foundation and the European Regional Development Fund, project 3.2.0101.11-0029, Centre of Excellence Mesosystems: Theory and Applications.http://www.elsevier.com/locate/physdhj201

Comparison of two models for phonon assisted tunneling field enhanced emission from defects in Ge measured by DLTS

Deep Level Transient Spectroscopy (DLTS) was used to measure the field enhanced emission rate from a defect introduced in n-type Ge. The defect was introduced through low energy (±80 eV) inductively coupled plasma (ICP) etching using Ar. The defect, named EP0.31, had an energy level 0.31 eV below the conduction band. Models of Pons and Makram-Ebeid (1979) [2] and Ganichev and Prettl (1997) [3], which describe emission due to phonon assisted tunnelling, were fitted to the observed electric field dependence of the emission rate. The model of Pons and Makram-Ebeid fitted the measured emission rate more accurately the Ganichev and Prettl. However the model of Ganichev and Prettl has only two parameters, while the model of Pons and Makram-Ebeid has four. Both models showed a trasition in the dominant emission mechanism from a weak electron-phonon coupling below 152.5 K to a strong electron –phonon coupling above 155 K. After the application of a x2 goodness of fit test, it was determined that the model of Pons and Makram-Ebeid describes the data well, while that of Ganichev and Prettl does not.The South African National Research Foundationhttp://www.elsevier.com/locate/phys

Temperature-dependent current-voltage characteristics of Pd/ZnO Schottky barrier diodes and the determination of the Richardson constant

We report on a systematic investigation of temperature dependent current-voltage (I-V) characteristics of Pd/ZnO Schottky barrier diodes in the 30-300 K temperature range. The ideality factor was observed to decrease with increase in temperature, whilst the barrier height increases with increase in temperature. The observed trend has been attributed to barrier inhomogeneities, which results in a distribution of barrier heights at the interface. Using the dependence of saturation current values on temperature, we have calculated the Richardson constant (A*) which was investigated in the two distinct temperature regions: 140–200 K and 210–300 K and values 3 x10-12 of and 3x10-9 A cm-2 K-2 were obtained, respectively. A mean barrier height of 0.97 eV was obtained in the 140-300 K temperature range. Applying the barrier height inhomogeneities correction, the value of A* was obtained from the modified Richardson plots as 39.43 and 39.03 A cm-2 K-2 in the 140-200 K and 210-300 K temperature range. The modified Richardson constant (A**) has proved to be strongly affected by barrier inhomogeneities and dependent on contact quality.South African National Research Foundation (NRF) and the University of Pretoria.http://www.elsevier.com/locate/mssp2016-06-30hb201

Electronic properties of shallow level defects in ZnO grown by pulsed laser deposition

We have used deep level transient spectroscopy (DLTS) to characterise four defects with shallow levels in ZnO grown by pulsed laser deposition (PLD). These defects all have DLTS peaks below 100 K. From DLTS measurements and Arrhenius plots we have calculated the energy levels of these defects as 31 meV, 64 meV, 100 meV and 140 meV, respectively, below the conduction band. The 100 meV defect displayed metastable behaviour: Annealing under reverse bias at temperatures of above 130 K introduced it while annealing under zero bias above 110 K removed it. The 64 meV and 140 meV defects exhibited a strong electric field assisted emission, indicating that they may be donors

Electrical characterisation of electron beam exposure induced defects in silicon

The defects introduced in epitaxially grown p-type silicon (Si) during electron beam exposure were electrically characterised 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 metal deposition. This is called electron beam exposure (EBE) herein. After 50 minutes of EBE, nickel (Ni) Schottky contacts were fabricated using the resistive deposition method. The defect level observed using the Ni contacts had an activation energy of H(0.55). This defect has an activation energy similar to that of the I-defect. The defect level is similar to that of the HB4, a boron related defect. DLTS depth profiling revealed that H(0.55) could be detected up to a depth of 0.8 μm below the junction. We found that exposing the samples to EBD conditions without metal deposition introduced a defect which was not introduced by the EBD method. We also observed that the damage caused by EBE extended deeper into the material compared to that caused by EBD.National Research Foundation of South Africa.http://www.elsevier.com/locate/physb2017-01-31hb2016Physic