Weak Frequency Dispersion of <i>C–V</i> 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/Al 2 O 3 /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 × 10 13 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.