Al+ Implanted 4H-SiC: Improved Electrical Activation and Ohmic Contacts

Abstract

The p-type doping of high purity semi-insulating 4H-SiC by Al+ ion implantation and a conventional thermal annealing of 1950 °C/5 min has been studied for implanted Al concentration in the range of 1 x1019 - 8 x 1020 cm-3 (0.36 μm implanted thickness). Sheet resistance in the range of 1.6 x 104 to 8.9 x102 Ω, corresponding to a resistivity in the range of 4.7 x 10-1 to 2.7 x 10-2 Ωcm for increasing implanted Al concentration have been obtained. Hall carrier density and mobility data in the temperature range of 140–600 K feature the transition from a valence band to an intra-band conduction for increasing implanted Al concentration. The specific contact resistance of Ti/Al contacts on the 5 x1019 cm-3 Al implanted specimen features a thermionic field effect conduction with a specific contact resistance in the 10-6 Ωcm2 decade.