Al Implantation and Post Annealing Effects in n-Type 4H-SiC

Abstract

We investigated the post annealing effect of Al implantation in n-type 4H-SiC by using deep level transient spectroscopy (DLTS). The Schottky contacts were deposited on n-type epitaxial layer on 4H-SiC substrates and the effect of Al-implantation on the structures has been examined with and without post-annealing process. n-type epitaxial layer on a 4H-SiC substrate was implanted with Al-ion at an energy of 300 keV and a dose of 1.0 × 1015 cm–2. The effect of annealing has been studied by annealing the structures at 1700 C after ion implantation. DLTS measurements were performed before and after ion implantation, in order to determine the characteristics and magnitudes of the resulting electrical defects. Based on the DLTS measurement results, typical Z1/2 peak of SiC is obtained in reference samples without implantation. Z1/2 of the non-annealed samples had an energy level of 0.831 eV. The energy level was found to be deeper after the implantation whereas the capture cross section is about 60 times smaller and the trap concentration increases by a factor of 10. In other words, the Al-ion implantation clearly influenced the electrical characteristics of the sample and consequently also the DLTS measurement results. After post-implantation annealing, a new shallow defect (I2Al-A) was identified (∼0.028 eV) with a capture cross section of 1.9 × 10–21 cm –2 and a trap concentration of 4.8 × 1015 cm–3.