Nanoscale Capacitance–Voltage Characterization of Two-Dimensional Electron Gas in AlGaN/GaN Heterostructures

A simple technique for quantitative nanoscale capacitance–voltage ( C – V ) measurements has been developed and used to characterize the two-dimensional electron gas (2DEG) at the interface of AlGaN/GaN heterostructures. The measurements indicate change in confinement of the 2DEG at the AlGaN/GaN interface depending on the direction of the dc voltage sweep during C – V measurements, indicating surface state charging and discharging. Under UV illumination, the 2DEG increased significantly as inferred from the increase in threshold voltage of the nanoscale C – V scans, while no change in 2DEG confinement was observed.