The 25th International Conference on Amorphous and Nano-crystalline Semiconductors
August 18–23, 2013 Toronto, Ontario Canada
25th Anniversary Plenary Lecture IV
Chair: Reinhard Carius, Jülich Forschungszentrum
Substitutional Doping of Amorphous and Nanocrystalline Semiconductors
Walter Schottky Institut, Technische Universität München, Am Coulombwall 4, 85748 Garching, Germany
The discovery 40 years ago that hydrogenated amorphous silicon can be substitutionally doped with phosphorus and boron to create pronounced n- or p-type conduction was not only an unexpected scientific surprise but also has opened up the way for commercial applications such as thin film transistors and solar cells in the field of amorphous semiconductors. Because of this fundamental importance, many investigations have been devoted to a better understanding of this phenomenon, and it became clear that doping in amorphous silicon is fundamentally different than in its crystalline counterpart. Also attempts to achieve a similar doping in other amorphous semiconductors beyond the group IV materials Si, Ge, and C have been unsuccessful or inconclusive at best.
Also in modern nanotechnology, substitutional doping of semiconductor nanocrystals or nanowires has turned out to be more complicated than expected, and again numerous studies are under way trying to shed more light on the microscopic mechanisms governing this important process.
Using amorphous Si and Si nanocrystals as model materials, we will summarize fundamental experimental observations and theoretical concepts made and developed over the years to describe substitutional doping in disordered solids. The current understanding in these model systems may be helpful for a better control of electronic properties in other disordered semiconducting material systems of current interest.
Keywords: disordered network, nanocrystals, doping, substitutional donors, doping efficiency, auto-compensation.