Publication Date:
2016-03-05
Description:
Low temperature oxidation of silicon in plasma ambient is a potential candidate for replacing thermally grown SiO 2 films for surface passivation of crystalline silicon solar cells. In this work, we report the growth of silicon oxy-nitride (SiO x N y ) film in N 2 O plasma ambient at 380 ° C. However, this process results in trapping of interstitial oxygen within silicon. The impact of this trapped interstitial oxygen on the surface passivation quality is investigated. The interstitial oxygen trapped in silicon was seen to decrease for larger SiO x N y film thickness. Effective minority carrier lifetime ( τ eff ) measurements on n-type float zone silicon wafers passivated by SiO x N y /silicon nitride (SiN v :H) stack showed a decrease in τ eff from 347 μ s to 68 μ s, for larger SiO x N y film thickness due to degradation in interface properties. From high frequency capacitance-voltage measurements, it was concluded that the surface passivation quality was governed by the interface parameters (fixed charge density and interface state density). High temperature firing of the SiO x N y /SiN v :H stack resulted in a severe degradation in τ eff due to migration of oxygen across the interface into silicon. However, on using the SiO x N y /SiN v :H stack for emitter surface passivation in screen printed p-type Si solar cells, an improvement in short wavelength response was observed in comparison to the passivation by SiN v :H alone, indicating an improvement in emitter surface passivation quality.
Print ISSN:
0021-8979
Electronic ISSN:
1089-7550
Topics:
Physics
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