Self-Assembly Growth of In-Rich InGaAs Core-Shell Structured Nanowires with Remarkable Near-Infrared Photoresponsivity.

Understanding the compositional distribution of ternary nanowires is essential to build the connection between nanowire structures and their potential applications. In this study, we grew epitaxial ternary InGaAs nanowires with high In concentration on GaAs {111} substrates. Our detailed electron microscopy characterizations suggest that the grown ternary InGaAs nanowires have an extraordinary core-shell structure with In-rich cores and Ga-enriched shells, in which both nanowire cores and shells showed compositional gradient. It was found that In-rich nanowire cores are formed due to the Ga-limited growth environment, caused by the competition with the spontaneous InGaAs planar layer growth on the substrate that consumes more Ga than the nominal Ga concentration during the growth. Moreover, the composition gradient in the nanowires cores and shells is a result of strain relaxation between them. Our optoelectronic property measurements from prototype nanowire devices show a remarkable photoresponsivity under the near-infrared illumination. This study provides a new approach for designing and realizing complex nanowire heterostructures for high-efficiency nanowire-based systems and devices.