Weak Frequency Dispersion of C–V Characteristics of AlGaN/GaN Metal‐Insulator‐Semiconductor Devices Despite High Interface Trap Density

For AlGaN/GaN metal‐insulator‐semiconductor (MIS) devices, it is shown that there is a case where the frequency dispersion of the capacitance–voltage (C–V) characteristics is very weak despite a rather high insulator–semiconductor interface trap density. We fabricated metal/Al2O3/AlGaN/GaN MIS devices, and carried out C–V characterization of them. Although they exhibit very weak C–V frequency dispersion for 100 Hz–1 MHz, we found that, based on the conductance method, the insulator–semiconductor interface trap densities are rather high ≈3 × 1013 cm−2 eV−1. As a possible explanation, a double‐peak model is considered, which underlines the possibility that a high interface trap density does not necessarily lead to strong C–V frequency dispersion. The model can explain the observed weak C–V frequency dispersion, implying that it is not appropriate to naively discuss the interface traps only from the apparent C–V frequency dispersion.