Tuning surface reflectance and carrier lifetime of cone-shaped macropore structures obtained by platinum-assisted chemical etching of silicon

Metal-assisted chemical etching (MACE) with platinum nanoparticles (Pt-NPs) was used to produce cone-shaped macropore structures (CSMS) on the surface of p-type silicon substrates. A straightforward control of the macropore dimensions is readily obtained as the etching time is tuned during the MACE process. The surface reflectance is advantageously reduced in a wide wavelength range and a minimum of 6.6% was achieved for an etching time of 9 min. The impact of the etching current on the morphological and optical properties of the textured Si wafers was also studied, revealing a substantial decrease of the surface reflectance up to an etching current of 40 mA. Moreover, an increase of the effective minority carrier lifetime from 5.9 to 8.9 µs was obtained as the etching current increases from 5 to 50 mA, indicating a reduction of surface recombination with the enlargement of the macropores. Interestingly, the field-effect passivation of the CSMS was found to significantly increase the effective carrier lifetime by reducing the surface recombination.