Deep Level Transient Spectroscopy of Defects Introduced in Si and SiGe by Low Energy Particles

Ion implantation and plasma processing techniques are routinely used for the fabrication of semiconductor devices. In particular, these techniques employ low energy ions, which modify the electrical and optical properties of the semiconductor material, and, consequently, of the devices that are fabricated thereon, by creating defects in the semiconductor lattice. In this paper, we review our results on the electrical characterization of defects created in Si by low energy noble gas ions (He, Ne, and Ar) and hydrogen ions using deep level transient spectroscopy. The properties of defects introduced in Si1-xGex during ion etching and electron beam evaporation of metal contacts are also reviewed

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

Solid state reaction of ruthenium with silicon carbide, and the implications for its use as a Schottky contact for high temperature operating Schottky diodes

A thin film of ruthenium was deposited on n-type-4-hexagonal-silicon- carbide (4H-SiC) so as to studythe interface behaviour of the ruthenium Schottky contact with silicon carbide. Ruthenium (Ru) Schottkydiode dots were also fabricated by deposition of ruthenium on n-type-4H-SiC which had nickel as aback ohmic contact. The Ru-4H-SiC Schottky barrier diodes (SBDs) and thin films were both annealedisochronally in a vacuum furnace at various temperatures. Rutherford-backscattering-spectrometry anal-ysis of the thin film sample showed evidence of formation of ruthenium silicide (Ru2Si3) and diffusionof ruthenium into silicon carbide at annealing temperatures of 700?C and 600?C respectively. Ramananalysis of the sample that was annealed in a vacuum at 1000?C showed evidence of the formation ofgraphite, and Ru2Si3. Despite the occurrence of the chemical reactions and diffusion of ruthenium into4H-SiC, the SBDs were operationally stable up to the final annealing temperature of 1000?C

Microstructure evolution and diffusion of ruthenium in silicon carbide, and the implications for structural integrity of SiC layer in TRISO coated fuel particles

A thin film of ruthenium (Ru) was deposited on n-type 4H-SiC and 6H-SiC by electron beam deposition technique so as to study interface reaction of ruthenium with silicon carbide at various annealing temperatures, and in two annealing environments namely vacuum and air. The Ru-4H-SiC and Ru-6H-SiC films were both annealed isochronally in a vacuum furnace at temperatures ranging from 500 to 1000 C, and the second set of samples were also annealed in air for temperatures ranging from 100 C to 600 C. After each annealing temperature, the films were analysed by Rutherford Backscattering spectrometry (RBS). Raman analysis and X-ray diffraction analysis were also used to analyse some of the samples. RBS analysis of 4H-SiC annealed in a vacuum showed evidence of formation of ruthenium silicide (Ru2Si3) and diffusion of Ru into SiC starting from annealing temperature of 700 C going upwards. In the case of Ru-6H-SiC annealed in a vacuum, RBS analysis showed formation of Ru 2Si3 at 600 C, in addition to the diffusion of Ru into SiC at 800 C. Raman analysis of the Ru-4H-SiC and Ru-6H-SiC samples that were annealed in a vacuum at 1000 C showed clear D and G carbon peaks which was evidence of formation of graphite. As for the samples annealed in air ruthenium oxidation started at a temperature of 400 C and diffusion of Ru into SiC commenced at temperatures of 500 C for both Ru-4H-SiC and Ru-6H-SiC. X-ray diffraction analysis of samples annealed in air at 600 C showed evidence of formation of ruthenium silicide in both 4H and 6H-SiC but this was not corroborated by RBS analysis

Electrical Characterization of Metastable Defects Introduced in GaN by Eu-Ion Implantation

Gallium nitride (GaN), grown by HVPE, was implanted with 300 keV Eu ions and then annealed at 1000 oC . Deep level transient spectroscopy (DLTS) and Laplace DLTS (L-DLTS) were used to characterise the ion implantation induced defects in GaN. Two of the implantation induced defects, E1 and E2, with DLTS peaks in the 100 – 200 K temperature range, had DLTS signals that could be studied with L-DLTS. We show that these two defects, with energy levels of 0.18 eV and 0.27 eV below the conduction band, respectively, are two configurations of a metastable defect. These two defect states can be reproducibly removed and re-introduced by changing the pulse, bias and temperature conditions, and the transformation processes follow first order kinetics.The South African National Research Foundation, the Fund for Scientific Research, Flanders (FWO), the Concerted Action of the KULeuven (GOA/2009/006), the Inter-university Attraction Pole (IAP P6/42) and the Center of Excellence Programme (INPAC EF/05/005).http://www.ttp.net/0255-5476.htmlhb2016Physic

Comparison of nickel, cobalt, palladium, and tungsten Schottky contacts on n-4H-silicon carbide

We have investigated the current-voltage (I-V) characteristics of nickel (Ni), cobalt (Co), tungsten (W) and palladium (Pd) Schottky contacts on n-type 4H-SiC in the 300–800 K temperature range. Results extracted from I-V measurements of Schottky barrier diodes showed that barrier height (ФBo) and ideality factor (n) were strongly dependent on temperature. Schottky barrier heights for contacts of all the metals showed an increase with temperature between 300 K and 800 K. This was attributed to barrier inhomogeneities at the interface between the metal and the semiconductor, which resulted in a distribution of barrier heights at the interface. Ideality factors of Ni, Co and Pd decreased from 1.6 to 1.0 and for W the ideality factor decreased from 1.1 to 1.0 when the temperature was increased from 300 K to 800 K respectively. The device parameters were compared to assess advantages and disadvantages of the metals for envisaged applications.The Midlands State University and University of Pretoria.http://www.elsevier.com/locate/physb2019-04-15hj2017Physic

Electrical characterization of deep levels created by bombarding nitrogen-doped 4H-SiC with alpha-particle irradiation

Deep-level transient spectroscopy (DLTS) and Laplace-DLTS were used to investigate the effect of alpha-particle irradiation on the electrical properties of nitrogen-doped 4H-SiC. The samples were bombarded with alpha-particles at room temperature (300 K) using an americium-241 (241Am) radionuclide source. DLTS revealed the presence of four deep levels in the as-grown samples, E0.09, E0.11, E0.16 and E0.65. After irradiation with a fluence of 4.1 × 1010 alpha-particles-cm–2, DLTS measurements indicated the presence of two new deep levels, E0.39 and E0.62 with energy level, EC – 0.39 eV and EC –0.62 eV, with an apparent capture cross sections of 2×10–16 and 2×10–14 cm2, respectively. Furthermore, irradiation with fluence of 8.9×1010 alpha-particles-cm–2 resulted in disappearance of shallow defects due to a lowering of the Fermi level. These defects - minutes. Defects, E0.39 and E0.42 with close emission rates were attributed to silicon or carbon vacancy and could only be separated by using high resolution Laplace-DLTS. The DLTS peaks at EC – (0.55-0.70) eV (known as Z1/Z2) were attributed to an isolated carbon vacancy (VC).This work is based on the research supported in part by the National Research Foundation (NRF) of South African (Grant specific unique reference number (UID) 78838).http://www.elsevier.com/locate/nimb2017-03-31hb2016Physic

Solid State Reaction and Operational Stability of Ruthenium Schottky Contact-on-6H-SiC Under Argon Annealing

Thin films of ruthenium-on-6-hexagonal silicon carbide (6H-SiC) were analysed by Rutherford backscattering spectroscopy (RBS) at various annealing temperatures. Some thin film samples were also analysed by scanning electron microscope (SEM). RBS analysis indicated minimal element diffusion, and formation of ruthenium oxide after annealing at 500 oC. Large scale diffusion of ruthenium (Ru) was observed to commence at 700 oC. The SEM images indicated that the as-deposited Ru was disorderly and amorphous. Annealing of the thin film improved the grain quality of Ru. The fabricated Ru-6H-SiC Schottky barrier diodes (SBD) with nickel ohmic contacts showed excellent rectifying behaviour and linear capacitance-voltage characteristics up to an annealing temperature of 900 oC. The SBDs degraded after annealing at 1000 oC. The degradation of the SBDs is attributed to the inter-diffusion of Ru and Si at the Schottky-substrate interface.http://link.springer.com/journal/116642016-10-31hb201