Schottky barrier height modification in Au/n-type 6H-SiC structures by PbS interfacial layer

Abstract

We have prepared the Au/PbS/n-6H-SiC Schottky diodes with interface layer and the reference Au/n-6H-SiC/Ni Schottky diodes without interface layer to realize Schottky barrier height (SBH) modification in the Au/SiC Schottky diodes. The BH reduction has been succeeded by the PbS interlayer to modify the effective BH by influencing the space charge region of the SiC. The PbS thin layer on the SiC was formed by the vacuum evaporation. The SBH values of 0.97 and 0.89 eV for the samples with and without the interfacial PbS layer were obtained from the forward bias current-voltage (I-V) characteristics. X-ray diffraction (XRD) study was carried out to determine the structural formation of the PbS on SiC. The reduction of the BH in the Au/PbS/n-6H-SiC Schottky diodes has been attributed to the fact that the interface states have a net positive interface charge in metal/n-type semiconductor contact, and thus the positive space charge Qsc in the Au/PbS/n-6H-SiC Schottky diodes becomes smaller than if the interface state charges Qss were absent. The experimental carrier concentration value of 4.73 × 1017 cm -3 obtained from the forward and reverse bias capacitance-voltage characteristics for the Au/PbS/n-6H-SiC contacts is lower than the value of 5.52 × 1017 cm-3 obtained for the reference diode, and this is an evidence of the reduction of the BH by the modification of the space charge density of the SiC. © 2010 Elsevier B.V. All rights reserved.