Group IV semiconductors lie at the heart of many electronic and photovoltaic devices. Issues associated with bulk silicon continue to be important, but substantial fundamental challenges also exist for other group IV bulk materials and associated alloys, nanostructures, nanocomposites, thin/thick films, and heterostructures. Advances in device performance are underpinned by new defect engineering procedures, development of novel growth techniques, and improvements in advanced diagnostic tools. Point and extended defects remain at the centre of interest, as do surfaces, and in some cases their engineering represents an option for new functionalities. This special issue contains 16 technical articles arising from selected presentations at Symposium I of the European Materials Research Society Spring Meeting held in Strasbourg, France from 18th to 22nd June 2018. This symposium was the third in the “Materials Research for Group IV Semiconductors” series. The symposium attracted 113 presenting authors from 22 countries, and 120 presentations were scheduled over five days (21 invited talks, 35 contributed talks, and 64 posters). Graduate Student Awards were presented to Audrey Morisset (Université Grenoble Alpes − INES, France) whose paper is published in this special issue, and Michael Seifner (TU Wien, Austria). In this special issue there are two feature articles from invited speakers in the silicon field. One by Hourai et al. reviews, from an industrial perspective, the development of point defect-controlled Czochralski silicon crystals and their use in power devices. The second by Kolevatov et al., focusses on the interaction between hydrogen and vacancy-related defects in silicon. The other papers cover a range of topics including the fundamentals of heat flow and transfer in semiconductors, the fundamental properties of point-like defects, surface passivation, potential new manufacturing methods, and a variety of novel heterostructures. Thanks are due to the symposium co-organisers (Chioko Kaneta, Gudrun Kissinger, Leo Miglio and Deren Yang), the members of our Scientific Committee, and the paper reviewers. We were particularly saddened to learn that Prof. Bengt Svensson, a Scientific Committee member and committed supporter of the symposium series over many years, died shortly after the symposium. An obituary to Bengt written by his colleagues and friends also appears in this special issue. John D. Murphy Guest Editor and Principal Symposium Organizer