Eero Jääskeläinen

The development of GaN-based blue light emitting diodes (LEDs) in the 1990s revolutionised all fields of illumination, leading to great energy savings and enabling new applications. By adding aluminium to GaN, the semiconductor’s band-gap can be increased to within the ultraviolet region, positioning AlGaN as the natural material candidate for UV-LEDs. The mass adoption of UV-LEDs has great potential for significant improvements in medicine, sterilisation, sensing, agritech, and many other fields.

However, the efficiency of UV LEDs is currently far lower than those operating in the visible region, owing largely to the difficulty in growing high-quality AlGaN crystals with low defect densities. This weakness remains especially pronounced in the UV-B range (280 nm to 310 nm), where state-of-the-art LEDs achieve efficiencies below 10%.

The introduction of nano-scale porosity into nitrides via electrochemical etching has been investigated in the group for several years. Among other promising applications of porous nitrides, the structural flexibility introduced by porosity can provide a mechanism for strain relaxation. My project will target the ‘UV-B gap’ of LEDs by leveraging porous AlGaN to reduce strain and thereby minimise defect density in the active region of the LED. My research has a strong focus on device realisation, and I endeavour to demonstrate the feasibility of porous AlGaN for strain relaxation with a complete LED device.

I joined the group as a PhD student in January 2025, with a background in semiconductor and condensed matter physics. My research is funded by the Ernest Oppenheimer Studentship.