Relevance of atomic collisions in low-dimensional structure physics

Ion-irradiation is employed routinely for the fabrication and analysis of electronic and optoelectronic materials structures. This includes species-dependent applications where the ion species is chosen for its electrical or chemical properties, such as: doping, alloying, and compound formation; and species-independent applications, where the choice of ion species is made out of convenience, such as: sputter etching, damage-induced electrical or optical isolation, compositional intermixing and ion-beam analysis. In all cases, radiation damage is an unavoidable consequence of the irradiation and plays a crucial role in determining the success of such processing. The radiation damage generated in semiconductor structures depends on many variables, including ion beam parameters such as: ion species, energy, fluence, and flux; and substrate parameters such as: substrate material, temperature and doping level. A basic understanding of these dependencies emerged early in the history of the subject but the details of radiation damage accumulation are extremely complex, even for the simplest of substrate materials; much remains to be understood. The problem is even more complex in multilayered, low-dimensional semiconductor structures, where a variety of different materials and multiple interfaces also influence the type, concentration and distribution of defects. This paper discusses the relevance of ion-irradiation to semiconductor materials processing and reviews recent experiments which have contributed further to our understanding or radiation damage production and its dependencies in such materials. The emphasis of the discussion is on the use of MeV ion-irradiation for damage-related device applications.