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

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posted on 12.08.2019, 19:33 by Shenghao Li, Manuel Pomaska, Jan Hoß, Jan Lossen, Mirko Ziegner, Ruijiang Hong, Friedhelm Finger, Uwe Rau, Kaining Ding
Hot-wire chemical vapor deposition was used to deposit in situ-doped amorphous silicon layers for poly-Si/SiOx 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.

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