Empirical Study of Hall Bars on Few-Layer Graphene on C-Face 4H-SiC

Abstract

Hall bars were fabricated on epitaxial graphene formed on 4H-SiC{0001} under various growth environments. Subsequently, they were analyzed via electrical characterization, atomic force microscopy (AFM), Raman mapping, and transmission electron microscopy (TEM) with emphasis on the C-face. The results of the measurement techniques were then corroborated to find correlations. It was found that there is a positive correlation between Hall mobility values and growth pressure in an Ar environment for the C-face. AFM elucidated that topographic features do not correlate with Hall mobility values, nor does device height correlate with carrier concentration. Raman spectroscopy showed that there is a correlation between Hall mobility values and the 2D peak full-width at half-maximum, and a weak correlation with 2D peak position. Additionally, the spectra are sensitive to topographic changes and film discontinuities. Dark-field TEM found higher levels of contrast variation in the SiC〈0001〉 direction, representative of out-of-plane disorder, corresponding to a blue-shift in the 2D peak position. This disorder does not seem to strongly influence Hall mobility values, as it was found in the device with the highest measured Hall mobility: 18,700 cm² V⁻¹ s⁻¹.