Effect of the Schottky barrier height on the detection of midgap levels in 4H-SiC by deep level transient spectroscopy

The effect of the Schottky barrier height on the detection of the concentration of midgap defects using deep level transient spectroscopy (DLTS) is experimentally and theoretically studied for EH₆ and EH₇ defects in 4H-SiC. In this special case, the DLTS signal height for EH₆ and EH₇ increases with increasing barrier height and saturates at values above 1.5 and 1.7 eV, respectively. Below 1.1 eV, the DLTS peak completely disappears for both defects. The experimental data are explained by a theoretical model. The course of the quasi-Fermi level in the space charge region is calculated as a function of the reverse current through it, which is determined by the barrier height, and the reverse bias applied.