Mervi Paulasto-Kröckel

Marek Patocka

UWBG AlN and AlGaN are attracting increasing interest for next-generation power electronics, but their development involves major challenges in epitaxy, contacting and device design as material composition and device requirements become more demanding.

In this talk, we discuss key issues in AlGaN and AlN hetero- and homoepitaxy, emphasizing non-destructive characterization by X-ray diffraction together with electron and probe microscopies. We then address the formation of ohmic contacts between silicon-doped AlGaN and metal contact stacks, focusing on how annealing temperature affects the properties of the resulting junction. We will also share the latest TCAD modelling results on high Al content AlGaN/AlN vertical polarization doped field effect transistors (POLFETs) for power electronics applications and outline the key challenges and design approaches for pushing the performance toward material limits.

Mervi Paulasto-Kröckel is Full Professor at Aalto University’s School of Electrical Engineering in Finland. She leads the Electronics Integration and Reliability (EILB) group, focused on exploring innovative materials and design concepts for advanced electronics. Before returning to academia in 2008, she spent over 12 years in automotive semiconductor R&D in Germany. She has authored or co-authored more than 150 scientific papers.

Marek Patočka is a doctoral researcher in EILB group. His research is focused on the characterisation and fabrication of Al(Ga)N layers and devices. He received his MSc degree from Brno University of Technology in 2024.

Martin Calkovsky

Threading dislocations (TDs) are critical crystalline defects in GaN-based materials, significantly impacting the performance, reliability, and lifetime of electronic and optoelectronic devices. We present Revelios, a semi-automated, non-destructive crystalline defect metrology software prototype based on electron channeling contrast imaging (ECCI). Revelios SW prototype enables large-area acquisition, automated stitching, detection and classification of TDs into a-, c-, and a+c-types. Dislocation type is determined by combining data acquired at different diffraction conditions and analyzing the black-white contrast orientation with respect to the set diffraction vector. Validation against expert manual evaluation shows a detection accuracy of 94% and a classification accuracy of 79%. These results demonstrate that Revelios SW prototype provides a robust and scalable solution for high-throughput GaN defect metrology and could be suitable for epitaxial process optimization and manufacturing control. Automation significantly increases throughput and reliability, supports efficient quantitative TD analysis, and makes the methodology accessible to less experienced users.

Dr. Martin Calkovsky is an electron microscopy expert specializing in crystalline defect metrology. With over 9 years of experience, Dr. Calkovsky currently holds the position of Application Scientist at Thermo Fisher Scientific Brno, focusing on developing advanced metrology methods using scanning electron microscopy (SEM) techniques. Holding a Ph.D. from Karlsruhe Institute of Technology, he has a proven track record in methodology development for material contrast quantification. Dr. Calkovsky has also held positions at the Institute for Basic Science South Korea and Karlsruhe Institute of Technology and is proficient in FIB/SEM and TEM microscopy for materials analysis.

Matthias Muehle

Diamond is an ultra-wide bandgap semiconductor material, whose electric properties make it a great choice as p-type material for device integration. Further, diamond possesses the highest thermal conductivity, which also makes it a great choice for use and integration within thermal cooling solutions.

This talk discusses a familiar of diamond-based technologies that were developed by Fraunhofer USA, Center Midwest, Fraunhofer IFAM and Fraunhofer IMWS to address cooling challenges within the various components of a semiconductor system:
(1) A single-crystalline diamond nanomembrane technology is presented, which enables device integration of boron-doped diamond layers with other semiconductor materials through means of heterointegration.
(2) A polycrystalline diamond nanomembrane technology portfolio is presented, which can be used as thermal interface material or as heatsink.
(3) A copper-diamond composite material, produced by gel-casting and spark-plasma-sintering, that can be used as heatsink with thermal conductivity exceeding that of copper by 3x is showcased.

Matthias Muehle received the Diploma degree in physics from Technische Universität Dresden, Germany, and the Ph.D. degree in electrical engineering from Michigan State University, USA, in 2017. He is currently the Manager Diamond Technologies at Fraunhofer USA, Center Midwest (CMW), overseeing materials research of diamond for use in semiconductors, analytical electrochemistry, neurology and water treatment. He has 15 years of experience working in diamond synthesis, wafer fabrication and device applications. His personal research focus is on diamond growth for (ultra) wide bandgap semiconductor integration.