III-V compound semiconductor nanowires (NWs) have attracted significant attention as nanoscale light sources for integrated photonics due to their nanoscale size, good optical/electrical properties and efficient strain relaxation capability 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, length and composition, 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 . Recently InGaAs/InP MQW NW array LED on Si has been reported with promising performances . However, there is limited understanding on the material growth and properties of InGaAs/InP MQW nanowires . Furthermore, so far there are no reports on QW based single NW LEDs.
In this project, first, we have successfully grown highly uniform InP/InGaAs MQW NW array by metalorganic chemical vapour deposition (MOCVD) on the pre-patterned substrate defined by electron-beam lithography. From detailed high-resolution scanning transmission electron microscopy study, it is found that MQWs are formed in both radial and vertical directions of the NW and a unique lateral growth evolution process occurs during the MQW NW growth. Based on the above understanding, we designed and demonstrated the first single InGaAs/InP QW NW LEDs with. Intense electroluminescence successfully observed from the single NW LEDs at the axial peak wavelength of around 1.3 μm which is ideally applicable to the integrated photonics for telecommunication applications. Finally, we further improved the QW NW growth for array-based LEDs and demonstrated operation of array NW QW LEDs. For the future work we will perform investigation on their microstructure, optical and electrical properties.
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