Relation between Work Function and Structural Properties of Triangular Defect in 4H-SiC Epitaxial Layer: Kelvin Probe Force Microscopic and Spectroscopic Analyses
To understand the relation between work function and structural properties of sufficiently expanded triangular defects (approximately 250 μm in size) in the 4H-SiC epitaxial layer, Kelvin probe force microscopy (KPFM) and spectroscopic (micro-Raman spectroscopy and photoluminescence (PL)) analyses were performed. Spectroscopic analysis demonstrated that the triangular defect mostly contains the 3C polytypes and that it has internal stress, defects, and defect-induced carrier generation. The distinguishable areas in the triangular defects had different surface potential values from the 4H-SiC matrix, and this was explained by the work function difference, which comes from variations in electron affinity by the 3C polytype as well as the position variations of Fermi energy level in terms of electron concentration. In addition, tensile stress induced-surface disorder was discussed leading to variations in electron affinity. The mechanical properties of triangular defects measured by nanoindenter were significantly deteriorated via many dislocation arrays and stacking faults with many broken and/or strained bonds.