The build-up of damage in 4H SiC epitaxial layers implanted with 100 or 180 keV Al ions in the dose range of 10(13) to 10(15) cm(-2) has been studied by transmission electron microscopy (TEM) and Rutherford backscattering spectroscopy in the channeling mode (c-RBS). Implantations have been done at temperatures between room temperature and 800 degreesC and the samples have been analysed after implantation and after post implant anneals. In as implanted samples channeling results show that a major part of the damage can be avoided already at implantations at 200 degreesC, but complete removal of damage is not possible even at an implantation temperature of 800 degreesC. After post implant annealing at typically 1600 degreesC a distribution of planar faults are seen by TEM. The size is around 10 nm, but increases with increasing annealing temperature.