Papers by Keyword: SiC Bulk Growth

Abstract: The growth of large diameter silicon carbide (SiC) crystals produced by the physical vapor transport (PVT) method is outlined. Methods to increase the crystal diameters, and to turn these large diameter crystals into substrates that are ready for the epitaxial growth of SiC or other non homogeneous epitaxial layers are discussed. We review the present status of 150 mm and 200 mm substrate quality at Cree, Inc. in terms of crystallinity, dislocation density as well as the final substrate surface quality.

Abstract: 2D and 3D in-situ X-ray visualization was applied to study the behavior of the SiC source material during PVT growth under various growth conditions. Experiments were carried out in two growth chambers for the growth of 3 inch and 4 inch crystals. Growth parameters were varied in the gas room in terms of axial temperature and inert gas pressure. The study addresses the stability of the SiC source material surface. It is shown that a higher inert gas pressure (e.g. 25 mbar) inhibits an unintentional upward evolution of the SiC feedstock that interferes with the crystal growth interface. The latter is related to a suppression of a pronounced recrystallization inside the SiC source. For a low inert gas pressure (e.g. 10 mbar) it is concluded that the axial temperature gradient inside the source material needs to be decreased to less than ca. 10 K/cm.

Abstract: A set of single crystal growth experiments was performed in the new resistively heated two-heater furnace, which plays the role of an induction furnace with a moving coil. In this new experimental setup we are able to control the shape of the crystallization front, from flat to extremely convex. The positive results of the experimental tests differ significantly from prior discouraging interpretation of computational modeling results obtained by a commonly used software, previously presented in the literature. The essence of a new regulation of the temperature field during the crystal growth is a displacement of the maximum of the temperature field, which at the beginning of the growth is located close to the seed and it moves towards the source material as the crystal length increases. In this way, the crystallization front is heated with a similar intensity regardless the increasing crystal length.

Abstract: In this work the problem of growth rate decaying during growth is considered. A new design and growth profiles are suggested in order to reduce deviations of growth parameters during the process of growth.

Abstract: Several SiC bulk crystals were grown with erbium and ytterbium as doping materials. Erbium contents determined by secondary ion mass spectroscopy (SIMS) ranged from 1.2 · 1014 cm-3 to 1.04 · 1015 cm-3, while ytterbium contents were below SIMS detection limit. Photoluminescence (PL) investigations of the characteristic 4f-4f-transition lines revealed a reduced luminescence yield in highly nitrogen and aluminum co-doped samples. Also, samples without intentional co-doping grown on the C-face showed less luminescence intensity than those grown on the Si-face. A stabilizing effect of erbium doping on the 4H polytype was observed.

Abstract: Several highly aluminum doped SiC bulk crystals were grown with a modified PVT (MPVT) method. To facilitate 4H-SiC formation, growth was conducted on the C-face. The samples were investigated using Hall measurements in the Van-der-Pauw geometry. Lowest room temperature values for specific resistivities were 0.09 Ωcm for 6H-SiC and 0.2 Ωcm for 4H-SiC, which are to our knowledge the lowest values yet reported in literature. Thus, resistivity values of < 0.2 Ωcm, which are required for substrates in high power device applications, could be demonstrated for 4HSiC. Remarkably, in very highly doped samples the type of conduction could not be determined by Hall measurements.