Practically all microprocessors in the world are made from a semiconductor called silicon, and they can be found everywhere from computers to dishwashers and smart watches to cars. Today’s information society depends on microchips. According to European Commission, a trillion chips were produced worldwide in 2020. To increase its self-sufficiency, Europe is investing heavily in the development of semiconductor technologies, for example through the new European Chips Act.
Microchips based on electrical data transfer have been manufactured for decades and the demand for them continues. Now, new types of light-based micro circuits are arriving on their side with an advantage of increased functionality, such as higher data transfer rates. The utilization of light also creates opportunities for new properties: for example, light-based micro-systems can be used in detection and recognition of gasses and biomarkers. According to Heidi Tuorila, the challenge is to develop compact integrated solutions that would allow to pack large laboratory equipment on a single chip, which can then be carried for example in a smart watch.
“In the future your watch might be able to follow the concentration of different biomarkers in your blood without a separate trip to blood tests,” says Tuorila.
From the big perspective there is nothing new in the fabrication of extremely small features on silicon microchips though it requires large investments in advanced cleanrooms and equipment. With the light-based circuits, however, a whole bunch of new semiconductor materials are required as they are needed for the light sources on the chips. The joining of laser chips fabricated from these materials as a part of a larger silicon microchip circuit is one of the big challenges of the field.
In her doctoral research Heidi Tuorila works towards solving this problem by developing laser chip fabrication methods and various advanced structures for joining silicon and the new semiconductor materials together. The light guiding elements on these chips need to be aligned with each other with the precision of a few hundred nanometers, otherwise the light and subsequently the data leak out. Hundred nanometers equal ten thousandth of a millimeter.
”We need to be able to ensure the compatibility of the materials and structures in a scale that is way too small for us to be able to touch the chips directly without crushing them. Sometimes a simple sounding task of joining two parts together turns out seemingly impossible when the tip of a pin appears like a tree trunk in comparison to the structures of a laser when viewed under a microscope,” says Tuorila.
What is also special in Tuorila’s work is the wide range of development and research between various types of materials. The different materials allow the introduction of different applications, and the solutions developed in the thesis serve a wide range of applications.
Heidi Tuorila carried out her doctoral dissertation research at the Optoelectronics Research Centre (ORC) at Tampere University under the supervision of Professor Mircea Guina and Dr. Jukka Viheriälä. The research work benefited from an intense collaboration with silicon-photonics group at VTT and Tyndall Institute in Ireland, being financed by several EU projects, Business Finland and PREIN Flagship.
Public defence on Thursday 14 November
The doctoral dissertation of MSc (Tech) Heidi Tuorila in the field of photonics titled “Advanced GaAs, InP and GaSb optoelectronics for hybrid photonic integrated circuits” will be publicly examined at the Faculty of Engineering and Natural Sciences at Tampere University at Thursday 14th November 2024 at Hervanta campus, Tietotalo and auditorium TB109 (Korkeakoulunkatu 1, Tampere).
The Opponent will be professor Ilkka Tittonen from Aalto University. The Custos will be Professor Mircea Guina from the Faculty of Engineering and Natural Sciences at Tampere University.