Fig. 4: Ferroelectric response of AlN grown on GaN.

a J–E loop of sputtered 100-nm-thin AlN grown on GaN measured at 40 kHz. b J–E loop of 5-nm-thin Al(Ga)N grown by MOCVD on GaN measured at 2 kHz. The overall current response, including typical ferroelectric displacement current peaks (switching, black) and dielectric/leakage currents (non-switching, red), was recorded separately by pre-polarizing the capacitor to the respective polarity. All measurements were performed at room temperature using a voltage signal with a triangular waveform. The current response was averaged over 100 cycles.