论文部分内容阅读
Ti/Al/Au ohmic contacts to p-type 4H-SiC in terms of a different annealing time and Ti composition are reported.At 1050℃,proper increase in annealing time plays a critical role in the Schottky to ohmic contact conversion.With the optimized annealing time,the contact with a high Ti content yields a lower specific contact resistivity(ρ_c) of 6.4×10~(-5)Ω·cm~2 compared with the low-Ti contact.The annealed surface morphology and phase resultants were examined by scanning electron microscopy(SEM) and X-ray diffraction(XRD),respectively.For the better ohmic contact,element distribution and chemical states were qualitatively identified by X-ray photoelectron spectroscopy(XPS) depth analysis.In particular,the presence of C and a Si-related phase was discussed and associated with the change in the surface status of the as-grown epilayer of 4H-SiC during annealing.The results reveal that the out-diffused C and Si atoms,with an approximate atomic ratio of 1:1 in the contact layer,can combine to form an amorphous Si-C state.The polycrystalline graphite instead of an unreacted C cluster in the whole alloyed structure and an extra nanosize graphite flake on the outermost surface of the annealed contact were confirmed by Raman spectroscopy.
Ti / Al / Au ohmic contacts to p-type 4H-SiC in terms of a different annealing time and Ti composition are reported. At 1050 ° C, proper increase in annealing time plays a critical role in the Schottky to ohmic contact conversion. Whith the optimized annealing time, the contact with a high Ti content yield a lower specific contact resistivity (ρ_c) of 6.4 × 10 ~ (-5) Ω · cm ~ 2 compared with the low-Ti contact. The annealed surface morphology and phase resultants were examined by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. For the better ohmic contact, element distribution and chemical states were qualitatively identified by X-ray photoelectron spectroscopy (XPS) depth analysis. of C and a Si-related phase was discussed and associated with the change in the surface status of the as-grown epilayer of 4H-SiC during annealing. These results reveal that the out-diffused C and Si atoms, with an approximate atomic ratio of 1: 1 in the contact layer, can combin e to form an amorphous Si-C state. The polycrystalline graphite instead of an unreacted C cluster in the whole alloyed structure and an extra nanosize graphite flake on the outermost surface of the annealed contact were confirmed by Raman spectroscopy.