Studies of 4H-SiC wafer and its epitaxial layers grown by chemical vapor deposition

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.