In Situ-Doped Silicon Thin Films for Passivating Contacts by Hot-Wire Chemical Vapor Deposition with a High Deposition Rate of 42 nm/min

Hot-wire chemical vapor deposition was used to deposit in situ-doped amorphous silicon layers for poly-Si/SiO_x passivating contacts at a high deposition rate of 42 nm/min. We investigated the influence of a varied phosphine gas (PH₃) concentration during deposition on (i) the silicon film properties and (ii) the passivating contact performances. The microstructural film properties were characterized before and after a high-temperature crystallization step to transform amorphous silicon films into polycrystalline silicon films. Before crystallization, the silicon layers become less dense as the PH₃ concentrations increase. After crystallization, an increasing domain size is derived for higher PH₃ concentrations. Sheet resistance is found to decrease as domain size increased, and the correlation between mobility and domain size was discussed. The performances of the passivating contact were measured, and a firing stable open circuit voltage of 732 mV, a contact resistivity of 8.1 mΩ·cm², and a sheet resistance of 142 Ω/□ could be achieved with the optimized PH₃ concentration. In addition, phosphorous doping tails into the crystalline silicon were extracted to evaluate the Auger recombination of the passivating contact.