These can be directly placed on semiconductors slice by CVD technique.

They have disadvantage of requiring extra processing step but also avoids necessity for uniform transport of dopant in vapor form to the slice.

In arrangement shown below, each dopant slice act as source for two adjacent microcircuit slices.

Typically 2-3 mm spacing is provided between each source and silicon slice. Uniform vapor transport occurs provided that spacing is held constant.

An advantage is that they require extremely simple gas handling system and presents no environmental problem with effluent handling.