The diffusion of silver in InP

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Abstract
The paper describes a large number of experiments in which radiotracer silver was diffused into the III-V semiconductor InP over a wide range of experimental conditions. Diffusion profiles were plotted. The diffusions were performed over the temperature range 550-900 degrees C for diffusion times between 2 min and 97 h. The ambient phosphorus vapour pressure was also varied over a wide range. Most of the experiments were carried out on undoped material, but doped n-type, p-type and semi-insulating materials were also used. The results cannot be explained by any simple diffusion theory and it would appear that a rather complex set of phenomena is in operation during the diffusions. The variation of surface concentration with phosphorus vapour pressure implies either that the silver atoms occupy phosphorus sites or that they are involved in some complex when occupying lattice sites. The latter explanation is considered the more likely and the complex (VpAgInVp) is proposed as a possibility. The very fast diffusion which is observed strongly suggests that the silver atoms diffuse in the interstitial state and the ion Ag1+ is proposed as the most likely. At lower diffusion temperatures most of the atoms in the bulk of the semiconductor probably remain interstitial, but at higher temperature, some of them join the lattice.
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