Electrical Characterization of 4H-and 6H-Silicon Carbide Schottky Diodes

摘要

The electrical properties of silicon carbide (SiC) make it an excellent candidatefor use in high temperature/high power devices due to its wide bandgap, high breakdown field, high electron mobility, etc. In this work two Schottky diodes of platinum (Pt) on n-type carbon faced 4H-SiC and three Schottky diodes of nickel (Ni) on n-type silicon faced 6H-SiC were electrically characterized. The diodes exhibited good performance up to 698 K for both the forward and reverse (up to -100v) bias voltages. The barrier heights measured by I-V-T tests were found to be 0.32 and 0.61 eV for the Pt/4H-SiC samples, but 1.08, 1.10, and 1.13 eV for the Ni/6H-SiC samples. Current voltage dependencies of thermionic and field emission were compared to theory and the diode current characteristics were found to have large tunneling and series resistance components. The series resistance for the Pt/4H-SiC and Ni/6H-SiC samples were determined to be about 70 ohms and 60 ohms, respectively. The ideality factors were found to decrease with temperature as predicted by theory, and ranged from n=3.2-1.6 and n=2.2-1.0 for the Pt/4H-SiC and Ni/6H-SiC samples, respectively. This determined that the Pt/4H-SiC diodes had a larger tunneling component. The Richardson's constant-active area products were found to be much smaller than theoretically calculated, indicating that the effective active areas much smaller than the contact and/or large quantum mechanical tunneling and reflection components are present. Capacitance tests revealed carrier concentrations of approximately 5x10(exp 16)/cu cm in the Pt/4H-SiC samples and 3x10(exp 17)/cu cm in the Ni/6H-SiC samples.