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

Abstract

We have systematically studied G 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 H-2 etched C-face and Si-face SiC wafers. The properties of ohmic contact formed on the backside of the G and Si-face wafers by metallization are investigated by ONM and AFM to observe the effect of G 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 G 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. (c) 2006 Elsevier B.V. All rights reserved.