MARCELO RIZZO PITON Development of Semiconductor Nanowire Materials for Electronic and Photonics Applications Tampere University Dissertations 189 Tampere University Dissertations 189 MARCELO RIZZO PITON Development of Semiconductor Nanowire Materials for Electronic and Photonics Applications ACADEMIC DISSERTATION To be presented, with the permission of the Faculty of Engineering and Natural Sciences of Tampere University, Finland and the Center of Exact Sciences and Technology of Federal University of São Carlos, Brazil for public discussion in the Swieca Room of the Physics Department Building, at Federal University of São Carlos, Rodovia Washington Luís, s/n, São Carlos-SP, Brazil on 5th of December 2019, at 10 o’clock. ACADEMIC DISSERTATION Tampere University, Faculty of Engineering and Natural Sciences, Finland Federal University of São Carlos, Center of Exact Sciences and Technology, Brazil Responsible Associate Professor Professor supervisors Yara Galvão Gobato Mircea Guina Federal University of São Carlos Tampere University Brazil Finland Supervisors Senior Research Fellow D.Sc. (Tech) Teemu Hakkarainen Soile Talmila Tampere University Modulight Finland Finland Professor Helder V. A. Galeti Federal University of São Carlos Brazil Pre-examiners Senior Technologist Professor Giorgio Biasiol Erkki Lähderanta Italian National Research Council LUT University Italy Finland Examination Professor Associate Professor committee Mohamed Henini Iouri Poussep University of Nottingham University of São Paulo United Kingdom Brazil Researcher Adjunct Professor Luís Barêa Fábio Aparecido Ferri Federal University of São Carlos Federal University of São Carlos Brazil Brazil Associate Professor Professor Yara Galvão Gobato Mircea Guina Federal University of São Carlos Tampere University Brazil Finland The originality of this thesis has been checked using the Turnitin OriginalityCheck service. Copyright ©2019 author Cover design: Roihu Inc. ISBN 978-952-03-1382-1 (print) ISBN 978-952-03-1383-8 (pdf) ISSN 2489-9860 (print) ISSN 2490-0028 (pdf) http://urn.fi/URN:ISBN:978-952-03-1383-8 PunaMusta Oy – Yliopistopaino Tampere 2019 To my family: Elza, Osvaldo and Gabriela iii iv ACKNOWLEDGEMENTS Firstly, I express my gratitude to Prof. Dra. Yara G. Gobato for taking me in as doctoral student that was looking for a new adventure in the vast and interesting world of semiconducting materials. All the opportunities, teachings and counseling were without any doubt crucial for reaching this point where I stand. Little I knew at the time that returning to my beloved UFSCar for doctoral studies would open so many doors for me. I am very grateful to Prof. Mircea Guina for accepting me initially as an exchange student at ORC research group in Tampere University and later as a doctoral student on a double-degree agreement between UFSCar and TUNI. To be involved in a high level research center was immeasurably valuable for my education and research skills acquired during my doctoral studies. My huge thanks to Dr. Teemu Hakkarainen to all the friendship, counseling and countless teachings during doctoral studies. Also part of our glorious nanowire team from ORC, I thank Eero Koivusalo for providing excellent nanowire samples, high-precision wafer cleaving and all the diverse tasks that we performed. I also thank Dr. Soile Talmila for all the early teachings and guidance during my learning process of nanowires processing. In general, I am very grateful for the complete work environment that was presented for me at ORC. I had a great and friendly working experience where I could discuss my current research issues with experts from different areas. I also show my thanks to my co-supervisor Prof. Dr. Helder V. A. Galeti for all the patience and instructions during measurements, for taking great care of great part of the TEM imaging and always keeping everything calm. I thank all members from G.O.M.A. in UFSCar for the friendship and help during the endless struggles with properly aligning the optical components of the photoluminesnce setup and creating crazy designs for new laboratory equipment to be made by the physics department staff. I greatly acknowledge and thank all the collaborations partners that were of great importance for the results and publications that were a result of this thesis work. My special thanks for Prof. Dr. Ariano D. G. Rodrigues from the Physics Department at UFSCar for all the discussions and teachings regarding Raman spectroscopy of semiconductor materials in general and also for nanowires. Also my thanks for Dr. Turkka Salminen for the Microscopy Center at TUNI for the training v and support for SEM and Raman microscope. My humble appreciation for the technical and cleanroom staff from TUNI for keeping everything running smoothly: Ilkka, Mervi, Mariia, Pena and Jarno. I acknowledge the research funding agencies from Brazil, CAPES and FAPESP, for the scholarship and exchange program funding during my doctoral studies. I also acknowledge the financial support from the Academy of Finland Project NESP and NanoLight for partially funding my research in Finland. Finally, I acknowledge the financial support from the Finnish Foundation for Technology Promotion (TES). Now for the reader that had the curiosity to read the next page of this acknowledgements section, it comes the time for me to thank all my colleagues and friends that were directly or indirectly involved during my life as doctoral student. My cheers to all my great friends in São Carlos and all the mid-week or weekend barbeques: Alessandro, Pedrão, Quake, Roma, Alex, Ursão, Jacaré and anyone else I might have forgotten. Also my greetings to all my longer date friends from the cities of Jaú and Itapuí. I really miss all of those people on a daily basis and hope that life will bring us closer again one day. In Finland I made very special and long-lasting friendships inside and outside university environment that are worth of a lot of thanks. At ORC I always felt friend of everyone that I somehow interacted or not, but my special thanks for Eero, Riku, Kostiantyn and Jarno for all the beers, memes, laughs and teachings of Finnish culture (although I definitely regret learning the existence of some sauna games but also happy of never taking part of them). My cheers to all my friends outside university that kept a broad range of topics and all the fun that we had either on amazing travels or simple board/electronic games nights: Deepak, Jobin, Biju, Philipp, Josh, Draupathy, Silvia and everyone else. Also for having the chance of being part of the greatest fully-foreign Pesapällo team: Perus-Ulkomaalaiset. At last but not least, I acknowledge Kultainen Apina, the best pub in Tampere, for being the stage of countless after-work Fridays beers (other mid-week days might have happened, it is classified) with funny and productive discussions covering all range of topics. Kippis! Cheers! Saúde! vi ABSTRACT The thesis is concerned with study of GaAs nanowires fabricated on Si substrate. The possibility of growing III-V semiconductor materials directly on silicon in the form of nanowires is an attractive route to the integration of microelectronic, photonic and optoelectronic technologies. To this end, development of functional heterostructure require effective and controllable doping but the dopant incorporation mechanisms involved in nanowire growth can be quite different from the well-established semiconductors thin film technology. The interplay of the different dopant incorporation mechanisms and the competition between axial and radial growth can result in dopant concentration gradients in the nanowires. As a key technology development enabling the study of transport properties in nanowires, a method for fabricating electrical contacts on single NWs using electron- beam lithography is reported. On the other hand, the reduced dimensions and the quasi one-dimensional nanowire geometry are challenging factors for the fabrication of electrical contacts in the correct geometry for Hall effect measurement, which is traditionally used in planar film to determine the dopant concentration and carriers mobility. Therefore, alternative techniques were employed to gain an understanding of the dopant incorporation mechanisms. To this end, Raman spectroscopy and current-voltage analysis on single-nanowire were used to estimate the spatial distribution of the Be and Te dopants along the axial direction of GaAs nanowires. The study reveals that the dopant incorporation mechanisms are strongly affected by the growth conditions for both p-type and n-type GaAs nanowires, resulting in gradients of dopant concentration along the nanowires. Besides the carrier transport properties, the waveguide properties of semiconductor nanowires were explored in the area of chiral sensing and emission of circularly polarized light. By fabricating asymmetric gold layers deposited on the nanowires sidewalls and under the adequate experimental conditions an extrinsic optical chirality configuration is achieved. The results show a strong chiral behavior in both absorption and emission of the partially Au-coated nanowires, and paves the way for applications such as chiral sensing and emitting devices. vii viii RESUMO Neste trabalho, realizamos um estudo sistemático das propriedades óticas, elétricas e estruturais de nanofios de GaAs dopados crescidos por epitaxia por feixes moleculares em substratos de Si. A possibilidade de crescer materiais semiconductores III-V na forma de nanofiosdiretamente sobre silício é uma