Super-Nernstian potentiometric response of InN/InGaN quantum dots by fractional electron transfer

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.