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We demonstrate the change of the sign from negative to positive of the self-powered photovoltaic photocurrent in core–shell n-InGaN/p-GaN nanowire heterojunctions within the visible to UV wavelength range. Such dual-polarity photodetectors are of broad interest to provide extended functionalities for optoelectronic devices, starting with dual-wavelength photodetectors. The physics of the photocurrent sign reversal is understood by a well-balanced selective absorption and photocarrier generation, photocarrier transfer, and thermal excitation paths in the core–shell n-InGaN/p-GaN nanowire functional absorber with different bandgap energies and opposite inner- and surface energy band bendings. The basic dual-wavelength photodetector operation parameters are given. [ABSTRACT FROM AUTHOR]

The potentiometric response of InN/InGaN quantum dots (QDs) on Si (111) is experimentally studied and modeled as a function of the In content and morphology of the InGaN layer below the QDs due to the changing N flux in stationary plasma-assisted molecular beam epitaxy. For isolated core–shell InGaN nanowires formed for N-rich growth, sub-Nernstian response with Cl− anions as the test analyte is observed. For compact columnar InGaN layers formed in a very narrow range of N flux at the N-rich to metal-rich growth transition, a maximum super-Nernstian response of 100 mV/decade is achieved, provided the In content is high. With reducing N flux and In content, low super-Nernstian response and finally sub-Nernstian response are re-established for compact planar GaN layers. The maximum super-Nernstian response and the transition to sub-Nernstian response are quantitatively modeled by the quantum partition of electrons inside and outside of the QDs and consequent fractional electron transfer in the artificial chemical reaction of the QDs with the anions. [ABSTRACT FROM AUTHOR]

An efficient visible-light photoelectrochemical photodetector based on a compact In-rich n-InGaN layer activated by p-Cu2O microcrystals operating as photoanode in the self-powered mode is demonstrated. The photocurrent density of 80 µA/cm2 under one-sun illumination is more than 10 times larger than that of a bare InGaN layer. Moreover, the photocurrent density, responsivity of 0.8 mA/W, specific detectivity of 4 × 109 Jones, and response times of 5–8 ms are more than five times better compared to those of our previously reported nanowire counterpart. The excellent performance is attributed to maximized photocarrier separation in the built-in electric field of the internal p–n junction for fully depleted Cu2O microcrystals with maximized height and the planar geometry, guaranteeing unhindered diffusion of the electrolyte to and from the photoanode surface. [ABSTRACT FROM AUTHOR]