Coimplantation effects on the electrical properties of boron and aluminum acceptors in 4H-SiC

The effect of coimplantation of carbon (C) and boron (B)/aluminum (Al) or silicon (Si) and B/Al on the electrical activation of B/Al accepters in 4H-SiC was studied by Hall effect investigations. The free hole concentration is found to increase due to coimplantation of C/B or C/AI. Compared to it, coimplantation of Si/B or Si/Al reduces the free hole concentration. For room temperature-implantation, the optimum concentration of coimplanted C atoms is found to be [C]approximate to=1x10(18)/cm(3) for an implanted acceptor concentration of [B]=[Al]=5x10(18)/cm(3) A further increase of the free hole concentration is found by employing hot-implantation of C at 800 degrees C. The mechanisms, which alter the electrical properties of B/Al accepters due to C- or Si-coimplantation, are discussed.