Investigations of defects introduced in 4H-SiC n-type epitaxial layers by hydrogen DC plasma

Abstract

Hydrogen is known to passivate donor and acceptor levels in SiC bulk, and also at the surface by forming bonds with Si atoms. Introduction of H atoms can then improve the electrical performance of Schottky diodes by reducing the metal-SiC interface state density. However it is necessary to verify if H-related complexes are formed or not, creating trap centers and corresponding deep levels. In this work, the electrical characteristics of defects introduced near the surface of n-type 4H-SiC epitaxial layers by DC hydrogen plasma were investigated. C-V technique revealed a donor-nature defect located deeper than the projected range of W ions, emitting electrons at temperatures > 300 K. Two deep levels were detected by DLTS measurements after high implantation energies, while the defect concentration decreases and only one defect is detected after lower implantation energies. The activation energies are similar to the double defect RD1/2, associated to the vacancy pair V-C-V-Si. Cathodoluminescence spectra showed the existence of a peculiar luminescence peak related to H introduction, which intensity increases with plasma energy.