Impact of defect on I(V) instabilities observed on Ti/4H-SiC high voltage Schottky diodes
Résumé
Anomaly in current at low forward bias is observed for large-area Ti Schottky diodes on n type 4H-SiC. Random telegraph signal (RTS) measurements, carried out on these defective devices, show discrete time switching of the current. Thermal activation of RTS signal gives two related trap signature (activation energy and cross section). Frequency analysis, using power spectral densities (PSDs) numerically calculated, confirms the presence of an extended defect which presents different charge states (i.e. an extended defect decorated by punctual traps). PSDs show two cut-off frequencies proving the individual response of two traps. Simulations of the I-V characteristics using two barrier heights modulated by a Gaussian function which represents the defect distribution show a good agreement with the experimental results. Finally we note that there s a strong correlation between traps observed by telegraph noise techniques and excess current. (C) 2015 Elsevier Ltd. All rights reserved.