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

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 (C N ) which is supposed to be the main cause of the Kink effect. The major H5 trap seems to be gallium vacancy complex (V Ga –O N ). 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.