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Photon emitters, detectors and converters

Research areas:

Microwave photonics

Microwave photons are one of the main interaction media in solid-state quantum devices such as superconducting and semiconducting qubits. We study experimentally and theoretically microwave photons interacting with electrons in semiconductor nanostructures in the so-called circuit quantum electrodynamics (cQED) setup. For the electronic part of the system, we focus on using quantum dots that enable to build photodetectors and emitters in the microwave domain and strong coherent coupling between electric charge and microwave photons in the electrical circuits.

Close-up of an electronic chip.
A microwave photodiode device converting microwave photons into an electrical current. By W. Khan.

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Key publications:

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.

Collage of photo and illustration of light-emitting diodes
Charge carrier diffusion induced NW-LEDs

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Making and characterisation of semiconductor micro-LED using cathodoluminescence

We grow pyramids of InGaN, which are converted to platelets, with following growth of quantum wells on the top, to make micro LEDs. All three basic colours: red, green and blue are now achievable. The morphology and the defects are investigated with the help of cathodoluminescence, which provides necessary spatial resolution to investigate these sub-micron structures.

grey and orange dots arranged in rows
Quantum well emission shows nice hexagonal emission patterns

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Key publications:

A. Gustafsson, et al, From InGaN pyramids to micro-LEDs characterized by cathodoluminescenceNano Express 2 (1) 014006 (2021)

M. Khalilian, et al, Coherently strained and dislocation-free architectured AlGaN/GaN submicron-sized structures, Nano Select 3 471–484 (2022)