The development of semiconductor materials and devices will lead to a new industrial technology revolution, in which the Silicon Carbide (SiC) substrate material has very excellent performance and it is especially suitable for manufacturing wave length lasers, white light emitting tubes, high-frequency, high-temperature and high-power devices, etc. This paper focuses on solving the key problems for producing large size and low defects of SiC crystals by the PVT method, such as the preparation and purification of the high purity raw material, the simulation of the temperature field, the control of the crystal defects and the growth of the large size SiC crystals.It is critical for the development of SiC industry.
Triangle-shaped defects are one of the most common surface defects on epitaxial growth of 4H-SiC epilayer on nearly on-axis SiC substrate. In this paper, we investigate the feature and structure of such defects using Nomarski optical microscopy (NOM), micro-Raman spectroscopy and high resolution transmission electron microscopy (HR-TEM). It is found that triangle-shaped defects were composed of a thick 3C-SiC polytype, as well as 4H-SiC epilayer.
The photoconductive semiconductor switches (PCSS) were fabricated on V-doped semi-insulating 6H-SiC. We studied the effect of surface morphology on the on-state resistance of SiC PCSS. The SiC wafers with quite similar physical properties were processed by mechanical polishing, chemical mechanical polishing and H2 etching for producing different surface morphologies. All the SiC PCSS were excited by a 355 nm laser with a frequency of 10 Hz and a pulse intensity of 132 μJ/mm2. We found that the surface morphology had an obvious effect on the on-state resistance. The PCSS fabricated on mechanical polished SiC wafer with an average surface roughness (rms) of 1.0 nm showed the largest on-state resistance of 45.6 ohms, while a low value of 13.3 ohms was observed for the wafer processed by H2 etching at high temperature of 1550 °C.
Gas etching and homoepitaxial growth on a nominally on-axis 2-inch 6H-SiC (0001) Si-face were studied. Regular steps with one unit cell height and complex pattern with facets and steps were observed after gas etching in the central region and edge region, respectively. The homoepitaxial growth shows that the complex (facets & steps) pattern expands and merges during the growth to bring on a rough epi-layer surface in the edge region. The steps with one unit cell height on the substrate split into steps with bilayers on the epilayer. The different lateral growth rates of <11-20>- and <1-100>-orientated steps make the width of steps orientated to <11-20> much larger than the ones orientated to <1-100>.
A competitive lattice model was developed for the Kinetic Monte Carlo (KMC) simulation of the competition of 4H and 6H polytypes in SiC crystal growth based on the on-lattice model. In the competitive lattice model, site positions are fixed at the perfect crystal lattice positions without any adjustment of the site positions. The effect of surface steps was investigated, and behavior similar to step-controlled homoepitaxy was observed in KMC simulation of PVT grown SiC. Maintaining the step growth mode is an important factor to maintain a stable single polytype during SiC growth.
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