Investigation of 4H-SiC layers implanted by Al ions

4H-SiC epitaxial layers 26 mu m thick with N-d-N-a=1 x 10(15) cm(-3) were grown by the CVD method on 4H-SiC commercial wafers. After CVD growth and investigations of the as-grown samples, the ion implantation doping (ID) with Al using ion energy of 150 keV with a dose of 5x10(16) cm(-2) was performed. Then a rapid thermal annealing for 15 s at 1700 degrees C was used to produce the p(+)n junctions. The initial CVD layers as well after ID and annealing were studied by combination of Xray diffractometry (XRD), local and image cathodoluminescence (LCL, CL image) and cross-sectional transmission electron microscopy (TEM). The inclusions of 6H and 3C polytypes with low density were found in initial 4H-SiC CVD layers. After Al ID the wide defective region about 20 mu m wide was detected, which was explained by summary of the radiation-accelerated diffusion of defects and "long-action effect" under irradiation. The short high temperature annealing led to formation of Al ID p+n junctions with complicated structure of p(+) -layer included polycrystalline surface and crystalline 4H-SiC areas. At the same time, the reduction of defective CL intensity from CVD layers compared to the original samples was revealed. This improvement of the structural quality of CVD layers after Al implantation and annealing was explained by "ion gettering" effect of defects from CVD layers near the interface.