Ru-Induced Deep Levels in Ru/4H-SiC Epilayer Schottky Diodes by Deep Level Transient Spectroscopy

Ru-induced deep levels in 50 mu m n-type 4H-SiC epitaxial layers were investigated by Deep Level Transient Spectroscopy (DLTS). Schottky diodes were fabricated by radio frequency (RF) sputtering thin layers of Ru metal on the epilayer surface and graphite paste for back Ohmic contact. Current-Voltage measurements (I-V) revealed a high barrier height of 1.70 eV and a diode ideality factor of 1.2 at room temperature (300 K). An effective carrier concentration of 4.34 x 10(14) cm(-3) was determined from a Mott-Schottky plot of the Capacitance-Voltage (C-V) measurements. DLTS studies revealed seven prominent defect levels at 0.12 +/- 0.02, 0.17 +/- 0.01, 0.65 +/- 0.01, 0.89 +/- 0.03, 1.26 +/- 0.04, 1.53 +/- 0.06, and 1.98 +/- 0.03 eV below the conduction band edge. Defect data reported in the literature suggests the new defect level of E-C -(0.89 +/- 0.03) eV may be correlated to Ru-induced defect formation in 4H-SiC epitaxial layer. The defect level observed at E-C -(1.98 +/- 0.03) eV has been observed for the first time in 50 mu m 4H-SiC epilayer following Ru Schottky barrier formation and subsequent rapid thermal annealing (RTA) and this deep level has not been reported elsewhere. (c) 2015 The Electrochemical Society. All rights reserved.