TY - GEN
T1 - Influence of the NH3:SiH4 ratio and surface morphology on the surface passivation of phosphorus-diffused C-Si by PECVD SiNx
AU - Wan, Yimao
AU - Yan, Di
AU - Cuevas, Andres
AU - McIntosh, Keith R.
N1 - Publisher Copyright:
© 2014 IEEE.
PY - 2014/10/15
Y1 - 2014/10/15
N2 - We investigate the surface passivation of phosphorus (n+) diffused crystalline silicon that is either planar or textured and passivated with amorphous silicon nitride (SiNx). A low and relatively constant saturation current density J0 is attained on the n+-diffused planar surfaces over a wide range of refractive index (n = 1.9-2.9 at 632 nm), and a wide range of sheet resistance (39-320 Ω/□). The results demonstrate that the trade-off between the optical transmission and surface recombination at n+-diffusion can be circumvented. That is, with careful optimization of SiNx properties, the optical advantages of SiNx can be enjoyed without penalty in recombination. In specific, on a light diffusion with sheet resistance of 700 Ω/□, a record-low J0 of 4 fA/cm2 is obtained using a nearly-stoichiometric SiNx with negligible absorption at short wavelengths. Moreover, it is shown that for lightly diffused surfaces, any additional recombination that occurs at textured surfaces relates strongly to the NH3:SiH4 ratio during the SiNx deposition, and consequently correlates inversely with n. In other words, an increase in the NH3:SiH4 ratio leads to an increase in recombination on planar wafers, and an even larger increase in recombination on textured wafers. By contrast, at the heavily-diffused surface, recombination at textured and planar wafers is approximately the same, irrespective of the NH3:SiH4 ratio. In summary, the results in this work indicate that the additional recombination invoked by the textured surfaces is greater as (i) the NH3:SiH4 ratio increases, which also increases n, and (ii) the phosphorus diffusion is lighter.
AB - We investigate the surface passivation of phosphorus (n+) diffused crystalline silicon that is either planar or textured and passivated with amorphous silicon nitride (SiNx). A low and relatively constant saturation current density J0 is attained on the n+-diffused planar surfaces over a wide range of refractive index (n = 1.9-2.9 at 632 nm), and a wide range of sheet resistance (39-320 Ω/□). The results demonstrate that the trade-off between the optical transmission and surface recombination at n+-diffusion can be circumvented. That is, with careful optimization of SiNx properties, the optical advantages of SiNx can be enjoyed without penalty in recombination. In specific, on a light diffusion with sheet resistance of 700 Ω/□, a record-low J0 of 4 fA/cm2 is obtained using a nearly-stoichiometric SiNx with negligible absorption at short wavelengths. Moreover, it is shown that for lightly diffused surfaces, any additional recombination that occurs at textured surfaces relates strongly to the NH3:SiH4 ratio during the SiNx deposition, and consequently correlates inversely with n. In other words, an increase in the NH3:SiH4 ratio leads to an increase in recombination on planar wafers, and an even larger increase in recombination on textured wafers. By contrast, at the heavily-diffused surface, recombination at textured and planar wafers is approximately the same, irrespective of the NH3:SiH4 ratio. In summary, the results in this work indicate that the additional recombination invoked by the textured surfaces is greater as (i) the NH3:SiH4 ratio increases, which also increases n, and (ii) the phosphorus diffusion is lighter.
KW - phosphorus
KW - photovoltaic cells
KW - silicon
KW - silicon nitride
KW - surface passivation
UR - http://www.scopus.com/inward/record.url?scp=84912061810&partnerID=8YFLogxK
U2 - 10.1109/PVSC.2014.6925644
DO - 10.1109/PVSC.2014.6925644
M3 - Conference contribution
T3 - 2014 IEEE 40th Photovoltaic Specialist Conference, PVSC 2014
SP - 3317
EP - 3321
BT - 2014 IEEE 40th Photovoltaic Specialist Conference, PVSC 2014
PB - Institute of Electrical and Electronics Engineers Inc.
T2 - 40th IEEE Photovoltaic Specialist Conference, PVSC 2014
Y2 - 8 June 2014 through 13 June 2014
ER -