Influence of annealing temperature on electrical parameters and structure of Al contacts on p-type 4H-SiC substrate
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In the paper we report the results of investigation focused on conditions of the ohmic contacts formation on p-type non-implanted 4H-SiC substrates. Aluminum layers were deposited, photolithographically etched and annealed at temperatures from 700 to 1000°C to obtain electrical contacts to SiC. On substrates annealed at temperatures 900 and 1000C the I-V characteristics confirmed ohmic type contacts formation. Lowest resistivity of fabricated contacts calculated using Circular Transfer Line Model (CTLM) was 2.64·10-4 Ωcm2. TOF SIMS profiling and RDX analysis were used to verify the microstructure of the Al/SiC interface. Ohmic contacts are characterized by an increased intensity of Si2- ion emission, which are characteristic for silicon nanocrystals, with respect to the emission from the pure SiC. This observation indicates that the ohmic nature of the received contacts can be affected by the presence of nanocrystalline silicon contact area. Presence of the nanocrystalline silicon has been also confirmed by XRD analysis.