An InN/InGaN quantum dot nonlinear constant phase element

InN/InGaN quantum dots (QDs) are found to establish a nonlinear constant phase element (CPE) response over a wide frequency range, measured by electrochemical impedance spectroscopy (EIS). The intrinsic surface donors together with the near-surface electron accumulation layer form the fractional capacitor. The magnitude of the impedance and the phase angle depend on the QD structural parameters and contact area. Importantly, they consistently change with applied voltage, constituting the nonlinear CPE response. A noise-filtering DC voltmeter with the phase angle as readout is proposed.