Papers by Author: M. Schmidbauer

Abstract: Single-crystalline 3C-SiC epitaxial layers were grown on on-axis Si (001) substrates by low-pressure hot-wall chemical vapour deposition. Aluminium from a trimethylaluminium (TMA) source was used for p-type doping. The atomic Al and carrier concentrations in the layers were determined as a function of the partial pressure of the TMA source gas. Secondary ion mass spectroscopy (SIMS), Hall-effect measurements at room temperature and four-point electrical resistivity method were applied to measure the atomic and electrically active Al concentrations. The crystalline perfection of the layers was characterized by high-resolution x-ray diffraction (HRXRD). At TMA-partial pressures ranging from 510-7 mbar up to 1.510-4 mbar corresponding aluminium concentrations from 21015 cm-3 up to 1.31019 cm-3 were measured in the epitaxial layers. On increasing the Al concentration from 1x1017 cm-3 to 1x1019 cm-3 the layer electrical resistivity decreases from 17 cm to 0.8 cm, while no influence on the crystalline quality of the layers was observed. The average full width at half maximum (FWHM) of the rocking curve for a 5µm thick 3C-SiC layer is about 500 arcsec. With increasing layer thickness (up to 16 µm) the FWHM of the rocking curve decreases to about 300 arcsec.

Abstract: 3C-SiC epitaxial layers were grown on on-axis Si (001) substrates by low-pressure hot-wall chemical vapour deposition. Depending on the growth parameters, the residual strain in the 3C-SiC layer was seen to be tensile or compressive. In this work, the influence of parameters, such as growth temperature and C/Si ratio in the vapour phase, on residual strain and macroscopic layer bow is investigated. We found that the wafer bow changes from convex, at a deposition temperature of 1270° C, to concave at 1370° C. High resolution x-ray diffraction data indicate that the crystal-line perfection of the layers is lower for decreasing deposition temperature and increasing compres-sive strain. No remarkable influence of the C/Si ratio in the gaseous atmosphere on the FWHM of the rocking curve was observed.

Abstract: The defect distribution in 4H-SiC single crystals in dependence on the seed polarity and its off-orientation was investigated by KOH-etching, optical microscopy and X-ray topography. Micropipe density, stacking fault density and dislocation density were determined for 2” crystals grown in <000-1> direction 0 - 7° off towards <11-20> and for crystals up to 1” in diameter grown in <11-20> or a- and <1-100> or m-directions and using repeated a-face growth. For the growth in polar directions the micropipe density and dislocation density decrease with increasing offorientation of the seed. A similar behavior was found for the stacking fault density and dislocation density in non-polar directions with off-orientation to c-direction. Nevertheless, while the dislocation density could be reduced up to three orders of magnitude for the growth along non-polar directions, the stacking fault density was continuously increasing. Additionally, the defect distribution after repeated a-face growth will be discussed in terms of growth related and kinetic models.