Electron Physics

Research topics
Complex thin films are a key enabler of a range of multiple multibillion Euro energy technologies - including energy efficient materials, energy generation and power electronics. Such different technologies share common metrology challenges related to quality, performance and reliability. More information at https://www.hymet.ptb.eu/
One of the major problems, which is currently limiting the state-of-the-art photovoltaic solar cells, is related to the material degradation under sun light. We study the possibility that the root cause for the degradation is related to the interaction of light with copper ions. Our approach could lead to a rather simple solution in avoiding power loss: implementing charge on the surface to attract the copper ions.
Black silicon absorbs light very efficienctly over a wide spectral range. The challenge of this material has been related to the surface passivation due to the increased surface area of the nanostructures. Our research is focused on the passivation of the black silicon by atomic layer deposition that allows very conformal coating.
Defects and impurities (e.g. oxygen, metals, dislocations, point defects) are most often harmful when present in semiconductor devices. With deep understanding of relevant defect reactions and gettering mechanisms, it is possible to tolerate the defects without affecting the device performance. Our studies include gettering e.g. by P/B diffusion, SiOx precipitates, Al layer, implantation. The applications can be either high purity silicon or solar grade / upgraded metallurgical silicon. Our research activities include also the development of characterization methods for defects, e.g. based on minority carrier lifetime.
Atomic layer deposition (ALD) technology has roots in Finland. In close collaboration with Beneq Oy, we study the fundamental passivation mechanisms of ALD thin films as well as develop the processes and equipment both in n-type and p-type cells.
Copper contacts have already taken place in microelectronics. Because of the cheaper price as compared to currently used silver, copper will most likely appear soon in commercial solar cells. Our silicon solar cell processing line includes copper metallization by sputtering or evaporation followed by electroplating. We study among other things the suitability of interconnecting ribbon to the copper contacts.
The group uses extensive clean room facitilites at Micronova Nanofabrication Centre for material research and device fabrication.
Latest publications
Role of CsMnCl3 Nanocrystal Structure on Its Luminescence Properties
Optoelectronic properties of black silicon fabricated by femtosecond laser in ambient air: exploring a large parameter space
Fast Wafer-Level Characterization of Silicon Photodetectors by Photoluminescence Imaging
Characterization of Heavily Irradiated Dielectrics for Pixel Sensors Coupling Insulator Applications
(oral talk) Record-high UV response in implanted junctions through passivation of surface defects and minimisation of boron implantation damage
Effect of anode sheet resistance on rise time of black silicon induced junction photodiodes
High-sensitivity photodiodes using black silicon and induced junction
(oral talk) Effect of anode sheet resistance on rise time of black silicon induced junction photodiodes
(poster) Spatial uniformity of black silicon induced junction photodiode responsivity
(poster) Reduction of defect density at Ge/Al2O3 interface using GeO2 interfacial layers
Contact:
Associate Professor Hele Savin
Email: hele.savin at aalto.fi
Tel.: +358 50 5410 156
Postal address:
Department of Electronics and Nanoengineering
Aalto University School of Electrical Engineering
P.O. Box 13500, 00076 Aalto, Finland
Visiting address:
Micronova, 4th floor, room 4156
Tietotie 3, 02150 Espoo