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Photonic devices

Within photonic devices, we fabricate and study controlled emission and detection of photons using semiconductor devices.

Project areas within Photonic devices



Lighting and displays account for a major part of our energy consumption, and presently light emitting diodes are penetrating the market. A first political incentive towards developing more efficient devices was taken by abolishing incandescent lamps. However, much more efficient and longer lifetime lighting devices are present today, constructed by the use of semiconductor-based light-emitting diodes.

By employing NW technology, further improvement in efficiency, material consumption, and material tuning can be achieved and the important application area of ultra-bright and high-resolution displays directly benefits from this nano-materials approach.

Nanowire-based micro-LEDs for display and lighting applications

At present, very strong efforts worldwide are focused on the possibility to replace virtually all display applications with micro-LEDs, as a next step after the market dominance of, first, liquid crystal-based displays and, later, OLEDs i.e. organic LEDs. In microLED display applications three basic colors, i.e. Blue, Green, and Red, are produced by optimally designed InGaN-LEDs, with dimensions such that the entire pixel is of the order, or smaller than, 10 µm. Such displays have inherent much higher brightness and efficiency than today’s technologies and are ideally suited for applications in the areas of VR/AR (virtual/augmented reality) or HUD (head-up displays for cars and airplanes).

For this research, we focus on sub-micron platelets of dislocation-free InGaN platelets enabling the direct and efficient emission of, not only blue but also green and red emission, all without the use of phosphor technology. We are, at the same time, investigating these RGB-controlled LEDs for, so-called, bio-centric lighting, by which the optimal color temperature can be obtained for various environmental situations. As a smaller, but important, area of LED applications, we carry on a minor effort in the field of UV-emitting LEDs of primary importance for water disinfection and general sterilization. 

Nanowire carrier diffusion induced light emitting diodes

Here we are working towards a nanowire light emitting diode architecture where the active parts do not have to be directly sandwiched in between electrical contacts but carrier diffusion from a higher band gap material into a lower band gap nanowire material can lead to highly polarized, directional and efficient luminescence. This is inspired by the work on carrier diffusion-induced luminescence in thin films done at Aalto University in Finland.


High-performance photodetectors for infrared radiation are key components in a large variety of optical systems. One primary application area in the NIR/SWIR regions is optical communication. The demand for wide bandwidth services such as social networking, streaming video, data mining, and ultimate exascale cloud computing is rising exponentially, exhausting the capabilities of copper-based circuitry employed in data centers.

Interconnect bandwidth, e.g. for I/O and clock distribution, is a major issue for high-performance computer systems. The Internet of Things (IoT) will bring sensors, appliances, and medical monitoring devices into the intelligent network with huge demands for bandwidth, increased compactness, and energy efficiency. 

Nanowire photodetectors

This project deals with the fundamental understanding and development of disruptive three-terminal wrap-gated nanowire (NW) array IR photodetectors for voltage-tunable broadband photoresponse in a single detector element. The proof-of-concept detectors combine our recent advances in growth of multiple quantum discs (QDiscs) in NWs, processing of NW array detectors, Fermi-level tuning in NWs using wrap-gates, tailoring of optical modes in photonic crystal structures, and monolithic integration of NWs with silicon.

Applying a bias to the wrap-gate facilities a Fermi-level tuning inside the discs, which in turn governs optical interband and intersubband transitions underlying the generation of an output detector signal. The detection of long-wavelength IR is hampered by two fundamental issues related to a low electric field intensity and fundamental selection rules for intersubband transitions.

Our preliminary studies have shown that embedding the NWs in designed dielectric waveguides promotes strong photonic crystal modes that solve both these issues. The detector geometry also serves as a platform for fundamental studies of optical effects related to a bias-tunable complex refractive index in strongly confined nanostructures.