AVS 53rd International Symposium
    Electronic Materials and Processing Monday Sessions
       Session EM-MoA

Paper EM-MoA5
Inhomogeneous Schottky Contacts on Silicon Carbide: Localized Fermi Level Pinning by Defects

Monday, November 13, 2006, 3:20 pm, Room 2003

Session: Contacts, Interfaces and Defects in Semiconductors
Presenter: L.M. Porter, Carnegie Mellon University
Authors: D.J. Ewing, Carnegie Mellon University
Q. Wahab, Linköping University, Sweden
M. Syväjärvi, Linköping University, Sweden
R. Yakimova, Linköping University, Sweden
S. Tumakha, The Ohio State University
M. Gao, The Ohio State University
L.J. Brillson, The Ohio State University
L.M. Porter, Carnegie Mellon University
Correspondent: Click to Email
Schottky barrier inhomogeneities, apparent as a knee in the low-voltage (Log I)-V characteristics, were present in a significant percentage of 4H-SiC diodes prepared from a variety of methods, sources, and contact materials. More than 500 Ni, Pt, or Ti diodes were characterized by a variety of techniques. Both commercially-produced chemical vapor deposited (CVD) epilayers and noncommercially-produced CVD and sublimation epilayers were used. The combined results from current-voltage measurements and modeling, electron beam induced current (EBIC), and site-specific and depth-resolved cathodoluminescence were used to develop a model to describe the relationship between specific defect states and the inhomogeneous behavior. By modeling the inhomogeneities as two Schottky barriers in parallel, high and low Schottky barriers were calculated for the non-ideal diodes. The high-barrier (ideal) barrier-heights for Pt, Ni, and Ti increased with metal workfunction with a slope parameter of 0.44, whereas the low barriers were predominantly centered at one of three values: 0.6, 0.85, and 1.05 eV. The site-specific and depth-resolved CL measurements of non-ideal diodes also revealed three different emission peaks (at 2.2, 2.4, and/or 2.65 eV), with the 2.4 eV peak originating from stacking faults observed in EBIC images; these peaks are the complements of the low barrier height values. Based on the results, the low-barrier barrier-heights can be explained by localized Fermi level pinning by specific material defects within the SiC epilayers. This model will be presented in terms of the defect level positions in the bandgap and their correspondence with the low barriers.