We present a dual experimental and computational studies on ruthenium (Ru) induced point defects in wide bandgap semiconductor 4H-silicon carbide (4H-SiC) which is of high interest in alpha, x-ray, and low energy gamma spectroscopy due to Ru’s high weighted metal work function of 4.76 eV which forms a high barrier Schottky contact with low leakage current. We first measured the activation energies and concentrations of deep levels in RF sputtered Ru/n-4H-SiC Schottky diodes annealed at 950°C using deep level transient spectroscopy (DLTS) and identified two deep level defects at Ec – (0.89 ± 0.03) eV and Ec - (1.98 ± 0.03) eV which appear unique to Schottky diodes with Ru. In order to correlate these defects theoretically, we then calculated the formation energies and transition levels of Ru induced point defects in 4H-SiC at charge states [-2, 2] for substitutions and [-2,+4] for interstitials using the projector augmented wave method (PAW) with both PBE and hybrid pseudopotentials on a 3 x 3 x 1 supercell. We found two transition levels which correlate very well with our experimental DLTS results. The transition (-1/0) for Ru substituted into the cubic silicon site at Ev + 2.39 eV and the transition (-1/0) for Ru placed in interstitial site with tetrahedral symmetry to carbon at Ev + 1.23 eV respectively.
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