Correlated optical and electrical analyses of inhomogeneous core/shell InGaN/GaN nanowire light emitting diodes.

The performance of core-shell InGaN/GaN nanowire light emitting diodes can be limited by wire-to-wire electrical inhomogeneities. Here we investigate an array of core-shell InGaN/GaN nanowires which are morphologically identical, but present electrical dissimilarities in order to understand how the nanoscale phenomena observed in individual nanowires affect the working performance of the whole array. The light emitting diode shows a low number of nanowires ( 20%) producing electroluminescence under operating conditions. This is related to a presence of a potential barrier at the interface between the nanowire core and the radially grown n-doped layer, which differently affects the electrical properties of the nanowires although they are morphologically identical. The impact of the potential barrier on the performance of the nanowire array is investigated by correlating multi-scanning techniques, namely electron beam induced current microscopy, electroluminescence mapping and cathodoluminescence analysis. It is found that the main cause of inhomogeneity in the array is related to a non-optimized charge injection into the active region, which can be overcome by changing the contact architecture so that the electrons become injected directly in the n-doped underlayer. The light emitting diode with so-called "front-n-contacting" is developed leading to an increase of the yield of emitting nanowires from 20% to 65%.