Diffusion of arsenic in germanium from the vapour phase

Abstract

The diffusion of arsenic in germanium has been measured. The diffusion constants and the concentrations of As at the surface in equilibrium with gaseous arsenic of a certain pressure have been determined at different temperatures. From the temperature dependence, the activation energy of diffusion and the pre-exponential constant have been calculated. It is found that, if the diffusion is carried out via the vapour phase and if the diffusion vessel contains zones of different temperatures, the surface concentration of the arsenic depends on the geometry of the vessel, when working in the absence of an inert gas. This effect is caused by the fact that the degree of dissociation of the gaseous As molecules above the germanium sample depends on the geometry of the vessel. A method is described how to get rid of thermal conversion.