DC and RF Local Electrical Properties of Macrostepped 4H-SiC Surface Probed by Scanning Spreading Resistance Microscopy and Scanning Microwave Impedance Microscopy Modes

Local electrical properties of a 4H-Silicon Carbide SiC(0001) 4°off macrostepped surface, obtained after liquid Si melting in a SiC/Si/SiC sandwich configuration, are investigated by Atomic Force Microscopy (AFM) in both DC and RF modes. On the same sample, macrosteps that are wide enough for allowing spatial resolution of the signal from terraces and step risers, but also some unreacted areas with standard flat surface (without macrosteps) are characterized. Scanning Spreading Resistance (SSRM, DC mode) reveals homogeneous conductivity on the wide terraces of the 4H-SiC(0001) macrosteps. On unreacted areas, which contain many step risers, the resistance is found higher than on the wide terrasses but it is also noisier. In addition, the AFM-RF scanning Microwave Impedance Microscopy (sMIM) mapping confirms the previous results by revealing lower conductivity on the unreacted areas than on the terraces of the macrosteps. Based on these results, some points defects located at the step risers which contribute negatively to the electrical properties of 4H-SiC(0001) surface are identified and electrically characterized.