Materials Science Forum Vols. 679-680

Abstract: A natural superlattice (NSL) in silicon carbide polytypes is shown to introduce a miniband structure into the conduction band, which leads to depressing of the electron impact zone-zone ionization at 300K with the electric field directed along the crystal axis or the NSL axis. The NSL influence can be also observed in the nitrogen impact ionization at 4.2K. In this case for the parallel field the impurity breakdown has not been fixed up to the fields 1.6 MV/cm in 6H-SiC. These results are explained by the insufficient gain in miniband for the ionization electron energy. Therewith the impurity breakdown at the electric field perpendicular to this axis correlates with a classical picture.

Abstract: In this article, using finite element simulations and analytical approaches, we demonstrate that planar rotators[1] can be effectively used to determine both the uniform and gradient residual stresses in thin films with higher accuracy compared to other microstructures.

Abstract: This work compares the piezoresistive properties of SiC thin films produced by two techniques enhanced by plasma, PECVD (plasma enhanced chemical vapor deposition) and RF magnetron sputtering. In order to study these properties, strain gauges based on SiC films produced were fabricated using photolithography techniques in conjunction with lift-off processes. The beam-bending method was used to characterize the SiC strain gauges fabricated.

Abstract: Micro-Raman spectroscopy has been used to study the dependence between the carrier concentration and electrical mobility in n-doped 3C-SiC films grown on (111) and (100) Si oriented substrates. Local stacking variations observed on the (111) 3C-SiC surface lead to a worse crystal morphology compared to (100) 3C-SiC films resulting in a decrease of the average bulk mobility.

Abstract: A brief overview about the recent progress in developing the methods to calculate the properties of defects in solids is given and some recent examples on vacancy-related defects in SiC are presented.

Abstract: Annealing of the Z1/2 and EH6/7 has been studied by DLTS after ion implantation of MeV Si ions and subsequent annealing in either N2 or O2 at 1150 °C, in the dose range 1 - 4 × 108 Si / cm2. It is found that the annealing rate of these prominent defects is greatly enhanced after thermal oxidation, and in particular close to the surface area, due to injection of a defect species which annihilates with both Z1/2 and EH6/7. The migration part of the diffusion coefficient of the injected defect is established to be in the range 1 – 2 × 10-8 cm2/s, and the measured concentration versus depth profiles of both Z1/2 and EH6/7 are accurately simulated by a simple model.

Abstract: Low doped epitaxial films of 4H SiC irradiated at 1 MeV and electron fluences of 1×1015 cm-2, 3×1015 cm-2 and 1×1016 cm-2 have been used to measure temperatures in two temperature intervals: 580°C to 640°C and 1220°C to 1320°C. Possible accuracy of the temperature measurements is judged to be better than 10 degrees Centigrade. Similar measurements should be possible from 100°C to 1500°C.

Abstract: The current communication focuses on the influence of a post-growth annealing on the evolution of defects inside (111) 3C-SiC layers grown by the Vapour Liquid Solid (VLS) mechanism in SiGe melts on Si-face on- and off axis 6H-SiC substrates. The layers are studied by Transmission Electron Microscopy (TEM) and Low Temperature Photoluminescence (LTPL). It was found that the growth on off-axis substrates results in a 3C-SiC layer containing mainly stacking faults (SFs) and microtwins (MT). The density of MT lamellae and SFs reduces in the layers grown on the on-axis substrate compared to off-axis substrate. In the layers grown on off-axis substrates the annealing strongly reduces the density of SFs inclined to the 3C/6H-SiC interface. Additionally, 3C to 6H polytypic transformation appears only at the interface, most probably starting from substrate step edges. This was only seen on off-axis seed since the step edges are more.

Abstract: The analysis of the donor-acceptor pair luminescence of P-Al and N-Al pairs obtained recently for the cubic 3C polytype of SiC is viewed in some detail. A detailed consideration is given to the fitting procedure applied to the P-Al and N-Al spectra. Fit with theoretical models of spectra of type I and type II are applied to both N-Al and P-Al experimental spectra, and it is demonstrated that only contribution from P on Si site is observable in the presented samples. The accuracy of the obtained phosphorus ionization energy of 48.1 meV is also discussed.

Abstract: DLTS measurements show bistable behavior of the previously reported EH5 peak in low- and high-energy electron irradiation 4H-SiC. Both reconfiguration processes (A ! B and B ! A) take place above 700 ±C. By isothermal annealing, the reconfiguration rates were determined and the reconfiguration energy was calculated to EA = 2.4±0.2 eV. Since the defect is present already after low-energy electron irradiation, which mainly affects the C atom in SiC, the EH5 peak may be related to defects associated with C-vacancies or C-interstitials