Reverse I–V–T analysis of Ti and Ni Schottky diodes on 6H-SiC with three contact areas

This work investigates the reverse-bias electrical behavior of Ti and Ni Schottky diodes fabricated on n-type 6H-SiC epitaxial layers, with contact areas of three different sizes: large (1.6 × 1.6 mm2), medium (1.6 × 0.4 mm2), and small (0.4 × 0.4 mm2). Reverse I–V–T measurements were performed over a broad temperature range (77–500 K) to examine the combined effects of metal type, contact area, and operating conditions on leakage current mechanism. In all diode types, the leakage current is influenced by temperature and reverse bias voltage, as well as by the nature of the metal contact and the size of the contact area. For Ti/6H-SiC diodes, the large and medium contacts followed nearly ideal thermionic emission behavior, while the small-area diode exhibited a pronounced increase in leakage current with both temperature and reverse bias voltage, indicating the contribution of additional transport mechanisms beyond pure thermionic emission. In contrast, for Ni/6H-SiC diodes, the large contact showed the expected thermally activated leakage current, whereas the medium and small contacts displayed leakage currents that were nearly independent of temperature, indicating enhanced thermal stability that can be attributed to a more uniform Schottky barrier. These results demonstrate that both contact area scaling and metal/semiconductor interface quality strongly affect the dominant transport mechanisms ranging from thermionic emission to trap-assisted tunneling (TAT), Poole–Frenkel, or Fowler–Nordheim tunneling, highlighting the complex interplay between geometry, material choice, and operating temperature in 6H-SiC Schottky diodes.