Semiconductor nanowires on flexible plastic substrates

Nanowires (NWs) offer exceptional potential for use in solar cells, lasers, LEDs, and photodetectors. In parallel, there's growing interest in flexible electronics due to their cost-effectiveness, lightweight design, mechanical resilience, and chemical stability. However, a major obstacle to integrating NWs with flexible electronics is the high temperatures typically required for metalorganic vapour phase epitaxy (MOVPE) growth, which makes NWs incompatible with most plastic substrates. This dissertation presents innovative techniques for the direct growth of III-V nanowires on flexible plastic substrates, along with methods to create functional nanowire-based flexible electronic devices. Firstly, this work establishes an isolated growth regime for self-catalysed InAs NWs, which enables their growth at record low temperatures. Extensive characterization reveals the ability to control crystal structure and NW density, which is particularly essential for achieving compatibility with lowtemperature processes necessary for flexible electronics. Next, the direct growth of III-V NWs on flexible plastic substrates is achieved. High-density, well-crystallized InAs and InP nanowires are grown on polyimide without pre-treatment, demonstrating strong mid-infrared emission for InAs and near-infrared emission for InP. Significantly, the electrical properties of these NWs allow for the fabrication of flexible nanowire-based p-n junction devices on plastic in just two fabrication steps. Additionally, this research marks the first successful growth of InSb nanowires on flexible plastic substrates. These NWs display high material quality, room temperature photoluminescence, and remarkable flexibility, showing promise for future flexible optoelectronics. Finally, a method for fabricating GaAs NW LEDs is presented. GaAs NWs are grown directly on flexible plastic substrates within the MOVPE reactor, showing zinc blende crystal structure, room temperature photoluminescence emission, and desirable optical properties. These findings open up possibilities for roll-to-roll compatible LED production using GaAs NWs, a key step in integrating these materials into a wide range of flexible optoelectronic devices. These advancements push the boundaries of flexible optoelectronics by enabling the direct growth of III-V nanowires on plastic substrates, while also lowering fabrication complexity and temperature requirements. The methods presented here pave the way for more versatile, durable, and efficient devices across a range of applications