Interface traps in insulator/AlGaN/GaN heterostructure capacitors

We have modeled and simulated capacitance voltage characteristics of metal/insulator/semiconductor heterostructure capacitor. The heterostructure was formed by AlGaN/GaN. Two types of distributions of interface traps in the AlGaN energy gap were used in our calculations and the two types of interface traps were assumed to be present at the insulator/AlGaN interface - an acceptor type and a donor type traps. The first one is obviously obtained in the upper part of the energy gap and the second one in the lower part of the gap. We obtained C-V characteristics with two capacitance steps which are sometimes obtained in experimental practice. The behavior and a shape of the C-V curves have been analyzed. The two steps in the characteristics correspond to the AlGaN and the GaN layers depletion. We observed also the stretching of the C-V curves as a result of interface traps presence in the structure.