Improved Ni ohmic contact on n-type 4H-SiC

• Published in: Journal of electronic materials 1997-03, Vol.26 (3), p.119-122
• Main Authors: Hallin, C., Yakimova, R., Pécz, B., Georgieva, A., Marinova, Ts, Kasamakova, L., Kakanakov, R., Janzén, E.
• Format: Article
• Language: English
• Subjects: Al/Ni/Al/4H-SiC - transmission electron microscopy - x-ray photoelectron spectroscopy; NATURAL SCIENCES; NATURVETENSKAP
• ISSN: 0361-5235; 1543-186X
• DOI: 10.1007/s11664-997-0136-2

This paper presents the structural, chemical and electronic properties of Al/Ni/ Al-layers evaporated on 4H silicon carbide and then annealed at 1000°C for 5 min. The structure was investigated before and after annealing by transmission electron spectroscopy from cross-sectional specimens. With x-ray photoelectron spectroscopy, both element distribution and bonding energies were followed during sputtering through the alloyed metal-semiconductor contact. Voids are found in both annealed Ni/4H-SiC and Al/Ni/Al/4H-SiC contact layers, though closer to the metal-semiconductor interface in the former case. The first aluminum-layer is believed to prevent voids to be formed at the interface and also to reduce the oxide on the semiconductor surface. The contact was found to be ohmic with a specific contact resistance ρ c - 1.8 × 10 −5 Ωcm 2 which is more than three times lower ρ c than for the ordinary Ni/4H-SiC contact prepared in the same way.