Papers by Author: Carole Balloud

Abstract: Cubic-silicon carbide crystals have been grown from solution by using the traveling-zone method. In this technique a molten silicon zone heated by induction coils is held between two rods of polycrystalline silicon carbide. Due to the growth set-up and boundary conditions, different mass transfer mechanisms are operative : diffusion, buoyancy, Marangoni convection and forced convection. The growth experiments have been performed on various seed crystals. Cubic SiC crystals were grown with a [111] habit on the [0001] silicon faces of 4H SiC seeds. The polytype 3C-SiC was identified by Transmission Electron Microscopy. Micro Raman spectroscopy and photoluminescence analyses showed good crystalline quality with few 6H inclusions.

Abstract: Because of the formation of DPB (Double Positioning Boundary) when starting from a hexagonal <0001> seed, DPB-free 3C-SiC single crystals have never been reported up to now. In a recent work we showed that, using adapted nucleation conditions, one could grow thick 3C-SiC single crystal almost free of DPB [1]. In this work we present the results of a multi-scale investigation of such crystals. Using birefringence microscopy, EBSD and HR-TEM, we find evidence of a continuous improvement of the crystal quality with increasing thickness in the most defected area, at the sample periphery. On the contrary, in the large DPB-free area, the SF density remains rather constant from the interface to the surface. The LTPL spectra collected at 5K on the upper part of samples present a nice resolution of multiple bound exciton features (up to m=5) which clearly shows the high (electronic) quality of our 3C-SiC material.

Abstract: Recently, a systematic comparison of SIMS measurements with LTPL (Low Temperature Photoluminescence) spectra led us to propose a straightforward empirical calibration of the LTPL intensity versus Al content in 4H-SiC samples. In the present work we analyze the effect of the LTPL excitation power on the intensity of the Al-related features. We examine the influence of the excitation conditions on the calibration curve and determine the limitations of the method.

Abstract: The evolution of defects versus thickness has been investigated in three different freestanding 3C-SiC samples, using TEM (Transmission Electron Microscopy) and LTPL (Low Temperature Photo-Luminescence) spectroscopy. In all samples, the stacking fault density reduces rapidly within the first 20 µm of the growth. Then it remains constant, at about 5x103 cm-1 up to the end. This behavior is attributed to the easy generation of stacking faults, even under a very low thermal stress, as in-situ experiments reveal. On the opposite the elimination of inversion domains, by bending boundaries during the growth, is found to be sample dependant. This is in good agreement with LTPL results.