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Fabrication of miniaturised and movable light-emitting diodes

Scientists have demonstrated the use of simple techniques to locally control nano-scale electrical properties and produce nano-sized light-emitting diodes (LEDs) with a bias control on the spatial position of the emitting area. This is relevant for several applications including Lab-On-a-Chip experiments, bio-imaging, high-resolution micro-displays and optoelectronic integrated circuits.
Fabrication of miniaturised and movable light-emitting diodes
LEDs the size of a pinhead are behind laser pointers and electronics displays. With the advent of nanotechnology, the quest for ever-more compact electronic and photonic devices is becoming a reality. Nano-LEDs are poised to revolutionise applications in high-resolution microscopy, ultra-high density information storage and even commercial lighting. Future high-volume production will require fast, flexible and cost-effective fabrication methods.

Scientists initiated the EU-funded project 'A novel approach to the fabrication of nanoscale light emitting diodes' (NANOLEDS) to exploit laser-driven diffusion of hydrogen (H) atoms in semiconductor LED structures, creating nano-scale channels for current flow. The miniature channels enable localised electrical and optical activations of sub-micrometre regions of the LED structure. Simultaneously, research increased the knowledge of the physics of hydrogen interactions in semiconductor alloys currently of intense interest globally.

Investigators demonstrated a strong modification of the electrical properties of gallium arsenide nitride (GaAsN) and gallium arsenide bismide (GaAsBi) alloys as a result of hydrogen diffusion, an effect that offers flexibility and control without lithographic or etching techniques. The direct laser writing approach to control nano-scale electrical properties will facilitate development of fast and easy fabrication techniques for nanotechnology. Researchers also demonstrated enhanced electrical properties in gallium manganese arsenide (GaMnAs)- and GaAs doped with carbon (GaAs:C)-based LED structures following hydrogen diffusion. Further, investigators have shown that the electrical effects of hydrogen introduction can be locally controlled for the realisation of nano-LEDs in GaAsN-based devices. Although difficulty in forming nano-scale channels was encountered due to defects and impurities, a shift in focus led to the fabrication of the first movable light-emitting area in an inorganic LED achieved by varying the voltage applied. It enabled accurate control of the location of the light-emitting area as well as a 10-fold increase in light intensity.

NANOLEDS made an important contribution to the large-scale and cost-effective fabrication of nano-LEDs, demonstrating excellent control over light-emitting localisation and electrical properties of the semiconductor materials employed. The direct laser writing method for controlling nano-scale properties paves the way to simple and flexible large-scale fabrication of nano-LEDs.

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