Influence of surface cleaning effects on properties of Schottky diodes on 4H-SiC

Ir/4H-SiC and IrO₂/4H-SiC Schottky diodes are reported in terms of different methods of surface pretreatment before contact deposition. In order to find the effect of surface preparation processes on Schottky characteristics the SiC wafers were respectively cleaned using the following processes: (1) RCA method followed by buffered HF dip. Next, the surface was oxidized (5.5 nm oxide) using a rapid thermal processing reactor chamber and circular geometry windows were opened in the oxide layer before metallization deposition; (2) the same as sequence (1) but with an additional in situ sputter etching step before metallization deposition; (3) cleaning in organic solvents followed by buffered HF dip. The I-V characteristics of Schottky diodes were analyzed to find a correlation between extracted parameters and surface treatment. The best results were obtained for the sequence (1) taking into account theoretical value of Schottky barrier height. The contacts showed excellent Schottky behavior with ideality factors below 1.08 and barrier heights of 1.46 eV and 1.64 eV for Ir and IrO₂, respectively. Very promising results were obtained for samples prepared using the sequence (2) taking into account the total static power losses because the modified surface preparation results in a decrease in the forward voltage drop and reverse leakage current simultaneously. The contacts with ideality factor below 1.09 and barrier height of 1.02 eV were fabricated for Ir/4H-SiC diodes in sequence (2).