Visualization of traps at SiO2/SiC interfaces near the conduction band by local deep level transient spectroscopy at low temperatures

Abstract

Local deep level transient spectroscopy (local-DLTS) at low temperatures is performed to investigate microscopic distributions of traps at SiO2/SiC interfaces near the conduction band. We find that the distributions of the density of interface states (Dit) with the energy depth of 0.20 eV from the conduction band edge show nonuniform contrasts with the scale of several hundreds of nanometers. We also apply local-DLTS to reveal the contribution of Dit to the nonuniform contrasts observed in scanning nonlinear dielectric microscopy (SNDM) images of SiO2/SiC samples. We analyze the cross-correlation between SNDM and Dit images obtained by simultaneous measurement with SNDM and local-DLTS, respectively. The patterns observed in the SNDM and Dit images simultaneously obtained at 150 K show a weak negative correlation, suggesting that nonuniform distributions of Dit contribute to the formation of inhomogeneous contrasts in the SNDM images.