2, Monash University, Clayton, Victoria, Australia
3, The Australian National University, Canberra, Australian Capital Territory, Australia
4, Cardiff University, Cardiff, , United Kingdom
5, The Australian National University, Canberra, Australian Capital Territory, Australia
III-V compound semiconductor nanowires (NWs) have attracted significant attention as nanoscale light sources in the integrated photonics due to their nanoscale size, good optical properties and strain relaxation feature enabling the monolithic growth on lattice mismatched substrates [1, 2]. In particular, NWs grown by selective area epitaxy (SAE) technique have many benefits such as controllability of their size and position, compatibility with silicon technology platform and high uniformity in diameter and length, facilitating the integration with other electronic devices. In addition to these advantages, a single standing NW itself can act as a vertical optical cavity  and an array composed of few tens to thousands of NWs also can act as a photonic crystal [4, 5], which is convenient for design of high power light emitting diodes (LEDs) and lasers. With suitable wavelength ranging from 1.3 to 1.6 μm and lattice matching of constituent materials, the InGaAs/InP multi quantum well (MQW) system has been being widely used for the optical communication devices . Nonetheless, there is limited understanding on the growth of InGaAs/InP MQW nanowires  and their application for LEDs has not reported.
In this work, we demonstrated the growth of highly uniform InP/InGaAs MQW NW array by metalorganic chemical vapour deposition (MOCVD) on the pre-patterned substrate defined by electron-beam lithography (EBL). The structural properties of the MQW NW were studied by aberration corrected high resolution scanning transmission electron microscopy (HR-STEM). The optical properties were characterized by micro photoluminescence (micro-PL) and cathodoluminescence (CL). From the HR-STEM study, it is found that MQWs are formed in both radial and vertical directions of the NW. From the in-depth microstructure analyses, we reveal a unique lateral growth evolution process occurring during the MQW NW growth which is induced by the phase difference between the InGaAs QW and barrier InP.
The InGaAs/InP MQW structure was further incorporated between the growth of a p- and n-InP segment for the formation of a diode. Single NWs were then transferred onto a SiO2-on-Si substrate and fabricated with Ti/Au electrodes. Based on the preliminary I-V measurements and electron-beam induced current (EBIC) characterisation, the fabricated single NW devices showed typical diode behaviour and EBIC also revealed a clear p-n junction location of the device. Further work is underway to optimise the growth and design of the p-i(MQW)-n diode structures for efficient MQW NW based LEDs.