Arsenic has a low misfit factor () and can be incorporated to a high concentration without causing strain the lattice. Arsenic's low diffusivity (about one-tenth of boron or phosphorous) and its abrupt doping profile makes it ideally suited for shallow diffused structures where more precise control of junction depth is needed. Phosphorus also has a high solid solubility and active carrier concentration close to arsenic. Its misfit factor also is small (). these characteristics makes its very useful for the fabrication of n+ regions in MOS and bipolar circuits.

Phosphorus, in the form of P₂O₅ , diffuses from the source to the wafer. When it reaches the silicon, it will undergo the following chemical reaction:

The phosphosilicate glass (PSG) is in contact with the silicon surface. A concentration gradient is formed, and since this process occurs at high temperature, diffusion will occur. The surface concentration will be fixed at the solid solubility, and the distribution will be in the form of a complimentary error function :