Very low surface recombination velocities on p- and n-type silicon wafers passivated with hydrogenated amorphous silicon films

Outstanding surface passivation of single-crystalline p- as well as n-type silicon is obtained using hydrogenated amorphous silicon (a-Si:H) films deposited at very low temperature in a plasma-enhanced chemical vapor deposition (PECVD) system. It is demonstrated that a-Si:H films with excellent surface passivation properties can be deposited in the temperature range between 200 and 250°C. Despite the low deposition temperature, the surface passivation of low-resistivity (∼1 Ωcm) p-type silicon provided by the films exceeds that provided by high-temperature (∼1000°C) thermal oxides and PECVD silicon nitride films deposited at temperatures around 400°C. A record-low surface recombination velocity (SRV) of 3 cm/s is achieved on 1.6-Ωcm p-Si. In addition, on 3.4-Ωcm n-Si wafers, very low SRVs of 7 cm/s are obtained. Investigations regarding the thermal stability of the passivation quality of the a-Si:H films show that the passivation is stable for temperatures exceeding the deposition temperature.