Réduction de la durée de vie des porteurs de charge dans le silicium noir par implantation ionique
The goal of this project is to study the effect of crystalline damage on the optoelectronic properties of photodetectors made from “black silicon” (i.e. femtosecond-laser microstructured silicon, which make it appear black).  Black silicon samples were annealed then implanted with either 300 keV Si+, 1500 keV Si+ or 2000 keV H+ ions.  The fluence used for the implantation was 1E11, 1E12 or 1E13 ion/cm2, resulting in nine different samples with a crystalline damage distribution of various depth and concentration.  Photodetectors were fabricated on these samples, together with a control detector made from a non-implanted black silicon sample and then characterized.  The I-V curves, spectral responsivities and frequency responses of the detectors were measured in short-circuit or under bias and compared.  The detectors display an approximately ohmic behavior, but those implanted at a higher fluence show a slightly better current rectification.  The implantation had a strong effect on the responsivity.  The external quantum efficiency increased from (0.069 ± 0.001) % at 900 nm for the control detector up to (26.0 ± 0.5) % for the 1E12 cm-2, 1500 keV Si+ detector.  With an applied bias of -0.50 V, the responsivity is increased and some detectors exhibit above unity photocurrent gain.  Similarly, the cutoff frequencies of the implanted detectors are higher.  A contactless experiment was attempted for the measurement of the effective carrier lifetime. The implantation damage was expected to reduce the carrier lifetime.  The setup didn’t meet all experimental conditions required to detect the signal using frequency-domain photo-induced reflection.
Black silicon Ion implantation Photodetector Characterization Lifetime