P-type 4H and 6H-SiC high-voltage Schottky barrier diodes

Abstract

High-voltage Schottky barrier diodes have been successfully fabricated for the first time on p-type 4H- and 6H-SiC using Ti as the barrier metal. Good rectification was confirmed at temperatures as high as 250/spl deg/C. The barrier heights were estimated to be 1.8-2.0 eV for 6H-SiC and 1.1-1.5 eV for 4H-SiC at room temperature using both I-V and C-V measurements. The specific on resistance (R/sub on,sp/) for 4H- and 6H-SiC were found to be 25 m/spl Omega/ cm/sup -2/ and 70 m/spl Omega/ cm/sup -2/ at room temperature. A monotonic decrease in resistance occurs with increasing temperature for both polytypes due to increased ionization of dopants. An analytical model is presented to explain the decrease of R/sub on,sp/ with temperature for both 4H and 6H-SiC which fits the experimental data. Critical electric field strength for breakdown was extracted for the first time in both p-type 4H and 6H-SiC using the breakdown voltage and was found to be 2.9/spl times/10/sup 6/ V/cm and 3.3/spl times/10/sup 6/ V/cm, respectively. The breakdown voltage remained fairly constant with temperature for 4H-SiC while it was found to decrease with temperature for 6H-SiC.