Photoresponse and Field Effect Transport Studies in InAsP–InP Core–Shell Nanowires

A ternary InAs_yP_1−y alloy is suitable for an application to near-infrared (NIR) optical devices as their direct bandgap energy covers the entire NIR band. A nanowire (NW) system allows an epitaxial integration of InAs_yP_1−y alloy on any type of substrate since the lattice mismatch strain can be relieved through the NW sidewall. Nevertheless, the very large surface to volume ratio feature of the NWs leads to enormous surface states which are susceptible to surface recombination of free carriers. Here, ternary InAs_0.75P_0.25 NWs are grown with InP passivation layer (i.e., core–shell structure) to minimize the influence of the surface states, thus increasing their optical and electrical properties. A photoresponse study was achieved through the modeled band structure of the grown NWs. The model and experimental results suggest that 5-nm-thick InP shell efficiently passivates the surface states of the InAs_0.75P_0.25 NWs. The fabricated core–shell photodetectors and field-effect transistors exhibit improved photoresponse and transport properties compared to its counterpart core-only structure.