Electrical Properties and Stability of Supersaturated Phosphorus‐Doped Silicon Layers

Supersaturated solutions of P in Si were obtained by ion implantation and pulsed ruby laser annealing. The dependence of electron mobility and electrical resistivity on carrier density was accurately determined by Hall effect and resistivity measurements. Maximum dopant concentration was 5 x 1021 atom/cm3, corresponding to a resistivity of 110 mu Omega .cm and to an electron mobility of 11 cm2/V.s. The stability of these alloys was analyzed by isochronal and isothermal annealing. In the more heavily doped samples a remarkable deactivation of the dopant was verified also for thermal treatments of 1 h at 300 deg C. TEM examinations showed a large amount of precipitates with density and size depending on supersaturation. Finally, it was observed that the electron mobility depends only on the carrier density and is unaffected by the electrically inactive P, even when present at very high concentrations.23 refs.--AA