Abstract
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.