Abstract: SiC technology is presently still burdened by a number of problems caused by process- or operation-induced defects. Experimental materials characterization in cooperation with atomistic modeling can be helpful in designing strategies against them. In recent years, considerable theoretical effort has been devoted to clarify the dynamics of defect creation and the mechanisms of dopant (de)activation. The investigation of epitaxial growth and of thermal oxidation has also begun. Here
an attempt is made to survey the most important theoretical results of the past four years from Europe.
Abstract: In a combined theoretical and experimental work, we have investigated the
common DI photoluminescence in 6H-SiC material. We present an atomistic model which is able to explain the annealing behavior, i. e. the correlation with the silicon vacancy, the local vibrational modes and the excitonic-like character observed.
Abstract: Positron lifetime spectroscopy was used to study defects in semi-insulating (SI) silicon carbide (SiC) substrates grown by high-temperature chemical vapor deposition (HTCVD). The measured positron lifetime spectra can be decomposed into two components, of which the longer corresponds to
vacancy clusters. We have carried out atomic superposition calculations to estimate the size of these clusters.
Abstract: This paper presents positron lifetime results which give information on the nature of
vacancy defects induced by electron irradiation in bulk nitrogen doped (nD-nA= 2.3x1017 cm-3) Cree 6H-SiC. The electron irradiations have been performed at different energies and with different fluences from 51017 e-cm-2 to 31018 e-cm-2. Positron lifetime have been measured with a 22NaCl source as a function of temperature between 15 and 300 K. The lifetime spectra were analyzed as sums of two exponential lifetime components i weighted by the intensities Ii, convoluted with the resolution function. From the temperature dependence of the lifetime spectra
we can infer that several vacancy defects exist in the electron irradiated n-type 6H-SiC. The nature of detected vacancy defects depends on the electron energy.
Abstract: We identify the VSiCSi(SiCCSi) complex in electron-irradiated 6H-SiC samples. Based on the analysis of new photo-excited EPR spectra, and supported by theoretical calculations, it was possible to establish its microscopic structure and to conclude that this complex is formed from the first product of the Si-vacancy annealing, the VSiCSi complex (also known as P6/P7 centers).
Abstract: Deep-Level Transient Spectroscopy and room temperature photoluminescence were used to characterise a 6H-SiC epitaxial layer irradiated with 10 MeV C+ and to follow the defect annealing in the temperature range 300-1400 °C. The intensity of luminescence peak at 423 nm, related to band to band transitions, decreases after irradiation and it is slowly recovered after annealing in the temperature range 1000-1400 °C. The DLTS spectra of low temperature annealed samples show the presence of several overlapping traps, which anneal and evolve at high
temperatures. After 1200 °C a main level at Ec-0.43 eV (E1/E2) is detected. The comparison between luminescence and DLTS results indicates that the defect associated with the E1/E2 level is mainly responsible for the luminescence quenching after irradiation.
Abstract: The high-temperature stable defect complexes in 6H-SiC crystals created by heavy
neutron irradiation and following high-temperature annealing have been discovered by EPR. After annealing at 1500°C at least five new axially symmetric centers with the electron spin S = 1/2 and S = 1 were shown to arise in 6H-SiC crystals. The striking feature of all discovered centers is a strong hyperfine interaction with a great number (up to twelve) of equivalent host Si (C) atoms. Two
models, a four-vacancy complex VSi-3VC, and a split-interstitial antisite (C2)Si or a pair of two antisites (C2)Si-SiC are discussed. There is a good probability that some of new centers could be related to the famous D1 and DII centers. After annealing at 2000°C the dc1-dc4 centers disappeared and a new triplet center labeled as N-V in the form of a silicon vacancy and a nitrogen atom in neighboring carbon substitutional position has been observed. The parameters of this center are
similar to that for well-known N-V center in diamond.
Abstract: A set of four lightly p-type 6H SiC boule samples was implanted with H or He and
annealed in isochronal stages from 950°C to 1500°C. Differences in the hydrogen, DI and DII low temperature photoluminescence spectra are observed and compared. Surprisingly, the hydrogen spectrum appears after a 1300°C anneal in the He implanted samples. A number of unidentified damage lines are also reported.