Low surface damage dry etched black silicon

Maksym M. Plakhotnyuk, Maria Gaudig, Rasmus Schmidt Davidsen, Jonas Michael-Lindhard, Jens Hirsch, Dominik Lausch, Michael Stenbæk Schmidt, Eugen Stamate, Ole Hansen

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Abstract

Black silicon (bSi) is promising for integration into silicon solar cell fabrication flow due to its excellent light trapping and low reflectance, and a continuously improving passivation. However, intensive ion bombardment during the reactive ion etching used to fabricate bSi induces surface damage that causes significant recombination. Here, we present a process optimization strategy for bSi, where surface damage is reduced and surface passivation is improved while excellent light trapping and low reflectance are maintained. We demonstrate that reduction of the capacitively coupled plasma power, during reactive ion etching at non-cryogenic temperature (-20°C), preserves the reflectivity below 1% and improves the effective minority carrier lifetime due to reduced ion energy. We investigate the effect of the etching process on the surface morphology, light trapping, reflectance, transmittance, and effective lifetime of bSi. Additional surface passivation using atomic layer deposition of Al2O3 significantly improves the effective lifetime. For n-type wafers, the lifetime reaches 12 ms for polished and 7.5 ms for bSi surfaces. For p-type wafers, the lifetime reaches 800 ls for both polished and bSi surfaces.
Original languageEnglish
Article number143101
JournalJournal of Applied Physics
Volume122
Issue number14
Number of pages9
ISSN0021-8979
DOIs
Publication statusPublished - 2017

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