We
have systematically studied C- and Si-face n-4H-SiC wafers before and
after the growth of epitaxial layers using an optical Nomarski microscope (ONM)
and an atomic force microscope (AFM). In particular, a number of defects such
as micropipes, microtubes, threading edge dislocations, and screw dislocations
are identified in H2 etched C-face and Si-face SiC wafers. The properties
of ohmic contact formed on the backside of the C- and Si-face wafers by
metallization are investigated by ONM and AFM to observe the effect of C- and
Si-face polarities. In addition to these analyses, X-ray diffraction studies
are done on the metallized Si- and C-faces to determine formation of any
silicides. Ni-based Schottky junctions made on the wafers and on the epitaxial
layers grown on the C- and Si-face 4H-SiC are studied by means of I–V and
capacitance–voltage (C–V) techniques. The difference in characteristics between
the Schottky junctions on the wafer and on the epilayer is analyzed. The C–V mapping
is done on several Schottky diodes, in order to find the effect of hillocks and
carrot-like defects in the junctions. The Schottky junction barrier heights
decreased if carrot-like defects are presented in the epilayer. The variation
of capacitance with temperature for the Schottky junctions is studied by using C–V measurements
and their results are discussed with effect of temperature.
Source:
Physica B: Condensed Matter
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