Characterization of high electron mobility transistor (HEMT) structures is important for predicting device behavior, monitoring and developing processes, and improving performance. Multifrequency capacitance–voltage (CV) and direct current–voltage (IV) methods are applied with a mercury probe to assess the HEMT with and without capping layers to monitor critical parameters such as pinch-off voltage, two-dimensional electron gas (2DEG) sheet charge, GaN carrier density profile, AlGaN thickness, and dielectric constant and properties of the top capping layer.
