Fabrication of 4H-SiC/nanocrystalline diamond pn junctions

Nitrogen-incorporated, n-type nanocrystalline diamond (NCD) films are deposited on p-type Si(001) and 4H-SiC(0001) substrates by moderate-pressure, microwave plasma-enhanced chemical vapor deposition using a mixture of 1%CH ₄-30%N₂-69%Ar. X-ray diffraction and visible Raman spectroscopy reveal that the structure of the NCD films is identical independent of the substrate materials, such that diamond nanoparticles with apparent crystal sizes of 5-8 nm are embedded in amorphous sp² carbon matrix. For p-Si/n-NCD heterojunctions in a diode configuration, the rectifying behavior in current-voltage curves depends upon the substrate temperature for film deposition, and the rectification ratio reaches a maximum of about 300 when the film is deposited at 830 °C. For p-4H-SiC/n-NCD heterojunctions, the rectification ratio increases greatly to about 10000 when the film is deposited at 830 °C due exclusively to suppression of the reverse leakage current.