Correlation between Kink effect and trapping mechanism through H1 hole trap in Al0.22Ga0.78N/GaN/SiC HEMTs by current DLTS: field effect enhancement

Abstract

A cryogenic investigation of the Kink effect with drain-source bias sweeping process during output characteristics is suggested. An exhaustive study of the field effect dependence on the emission rate from hole traps in AlGaN/GaN HEMT transistors has been realized by means of current DLTS spectroscopy (I-DLTS). We have found that the Kink effect was induced by impact ionization of electron trapped in acceptor-like deep levels with activation energies at about 0.85 eV overhead the valence band of the GaN buffer layer. Using I-DLTS method, three holes traps, labeled A, H1, and H5, have been distinguished. The H1 deep level might correspond to the carbon substituting the N site (CN) which is supposed to be the main cause of the Kink effect. The major H5 trap seems to be gallium vacancy complex (VGa–ON). For the hole trap H1, the phonon-assisted tunneling emission is the dominant mechanism for holes to escape from the trapping centers while for the H5 trap their field dependence shows a classical pure tunneling effect.