Impact on the Conductance Method of the Asymmetry in the AC Response Induced by Interface Trap Levels

The conductance method has been extensively used to analyze the dielectric-semiconductor interfaces by assuming a continuous density of the interface traps. If dangling bonds are dense at the interface, the wavefunction tails of electrons in the dangling bonds overlap each other to form a continuous density of interface traps. However, as the advanced fabrication process improves the interface quality, the interface traps become dilute. Hence, the density of interface traps may be interpreted as a composition of distinct peaks with less overlapping of trapped electrons, i.e., the discrete localized interface traps. In this regard, we assume that peaks apart from the Fermi level more than the thermal energy affect the conductance method. This is a novel approach to the conventional conductance method. Present model derived in this study is applied on the zirconium oxide - silicon interface fabricated using the atomic layer deposition. As result, we successfully reproduced the asymmetrical conductance in frequency spectrum and obtained the distribution of interface trap density with time constants correspondent to the extracted energy levels. Inclusion of the peak levels shows larger fluctuation in time constants, and the proposed method compensates underestimation in the conventional conductance method.