Here, we employ photoelectrochemical measurements to systematically investigate Mg doping of GaN nanowires. In this approach, nanowires are contacted simply by immersing as-grown nanowire ensembles into a liquid electrolyte. Complicated processing steps involving expensive facilities such as electron beam lithography are not required. Furthermore, such measurements provide directly an average value for the entire nanowire ensemble. More specifically, measurements of the open-circuit potential in the dark and under illumination (ΔOCP) allow the identification of the conductivity type, and a Mott-Schottky analysis of capacitance voltage measurements provides in addition the density of ionized dopants. In fact, both methods showed the expected transition from n-type to p-type conductivity with increasing Mg doping level, and the latter characterization technique allowed us to quantify the charge carrier concentration. Beyond the quantitative information obtained for Mg doping of GaN nanowires, our systematic and comprehensive investigation demonstrates the benefit of photoelectrochemical methods for the analysis of doping in semiconductor nanowires in general.
This work was carried out in collaboration with the Institute for Solar Fuels at Helmholtz-Zentrum Berlin.
Jumpei Kamimura, Peter Bogdanoff, Manfred Ramsteiner, Pierre Corfdir, Felix Feix, Lutz Geelhaar, and Henning Riechert, “p-type doping of GaN nanowires characterized by photoelectrochemical measurements,” published in Nano Letters, Feb. 6, 2017. doi: 10.1021/acs.nanolett.6b04560