Anomalous dopant diffusion

Point-defect ordering (e.g., vacancy-dopant pairs) leads to interesting complications. Preparation conditions themselves (e.g., oxygen partial pressure and temperature in oxides) thermodynamically define and control this defect content and structure. It is important to realize that point defects are thermodynamically allowed and defined they are not anomalous in the least. Therefore, undoped, high-purity compounds may exhibit sizable nonstoichiometry due to intrinsic point defects. Doping (intentional addition of an impurity) allows one to precisely control the point-defect content and nonstoichiometry and, thereby, the properties. Transport properties are influenced by the point defects. Electrical conduction (hole or electron transport) and solid state diffusion of atoms generally vary with the quantity and type of point defects. 

The eo-diffusion of As and B which had been implanted to doses of about lOl /cm, using energies which gave the same projected range, was investigated at 900 and lOOOC by measuring dopant and carrier profiles. A comparison of co-diffusion data, with the results which were obtained by the separate diffusion of each element, revealed anomalous effeets which could be explained by positing the formation of neutral donor-acceptor pairs. These complexes were mobile, with diffusivities that could be described by ... 

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