Microstructural interpretation of Ni ohmic contact on n-type 4H–SiC

Abstract

Electrical properties and microstructure of ternary Ge ∕ Ti ∕ Al ohmic contacts to p -type 4H-SiC Improved Ni based composite Ohmic contact to n-SiC for high temperature and high power device applications Using cross-sectional transmission electron microscopy ͑TEM͒, microstructural changes in Ni contacts on n-type 4H-SiC as a function of annealing temperature were investigated. From these results, the correlation between the microstructural change and electrical properties was interpreted. After annealing at 800°C, which yielded rectifying behavior, the silicide phases were formed, composed of Ni 2 Si and Ni 31 Si 12 . From the results shown in microbeam diffraction patterns, Ni 31 Si 12 remains at the surface and Ni 2 Si is dominant in the contact, indicating that Ni 2 Si started to grow at the interface through the outdiffusion of Si atoms. When the sample was annealed at 950°C, ohmic behavior was shown, and the layer structure was changed to a C-rich layer/Ni 2 Si/NiSi/n-type SiC. The NiSi phase was observed. These results imply that the composition of Si in nickel silicide at the interface with SiC increased with the increase of annealing temperature. The observation of the graphite phase at the surface indicates that the C atoms diffused out to the surface at 950°C. This leads to the formation of carbon vacancies, acting as donors for electrons. These suggest that the production of carbon vacancies plays a major role in the formation of ohmic contact through the reduction of the effective Schottky barrier height for the transport of electrons.

Rectification at Graphene-Semiconductor Interfaces: Zero-Gap Semiconductor-Based Diodes

“…During the sample preparation and before the graphene transfer, the wafers were cleaned using typical surface-cleaning techniques. Ohmic contacts to the semiconductors were formed using conventional Ohmic-contact recipes [12][13][14][15]. Multilayer Ohmic contacts were thermally grown on the back and front side of the semiconductor and were annealed at high temperatures using rapid thermal annealing.…”

“…However, using the extrapolated zero-bias saturation-current density, one can extract the SBH, and one can take into account the correction to the SBH at fixed bias (V) by the additional term ÁÈ SBH ðVÞ in Eq. (12).…”

Graphite based Schottky diodes formed on Si, GaAs, and 4H-SiC substrates

“…The substrates are thoroughly cleaned to remove any native oxide and/or contaminants. Ohmic contacts are made on the substrates using existing ohmic contact recipes [7,8,9].The HOPG contacts are made to the semiconductors using three related techniques: (1) spring loaded bulk HOPG, (2) Van der Waals adherence of cleaved HOPG flakes or (3) HOPG "paint". In the first technique a relatively large (∼1 mm 2 ) piece is gently pressed onto the substrate.…”

“…The substrates are thoroughly cleaned to remove any native oxide and/or contaminants. Ohmic contacts are made on the substrates using existing ohmic contact recipes [7,8,9].…”

Effect of annealing temperature on the contact properties of Ni/V/4H-SiC structure

“…5,6 Among all of these metals, Ni is regarded as the best metal to n-type 4H-SiC. [7][8][9] The specific contact resistance of Ni/SiC can reach as low as ∼10 -6 · cm 2 as reported by Rogowski et al 10 Ni can diffuse into SiC and form Ni x Si y compounds during rapid thermal annealing process. Among the Ni x Si y compounds, Ni 2 Si is considered as the key phase for making desirable ohmic contact.…”