Effect of Annealing of Silver Electrodes on Photolithographically Fabricated Silicon Trenches for Photodetection Applications

Abstract

The photosensitivity of metal–semiconductor–metal (MSM) ultraviolet photodetectors based on recessed electrodes on silicon (Si) substrate has been enhanced. Recessed electrodes were deposited in photolithography fabricated silicon trenches. Such recessed electrodes can collect photogenerated electrons beneath the silicon surface, hence increasing the photocurrent. For metallization of Si substrates to fabricate MSM photodetectors, two interdigitated silver (Ag) contacts were deposited for each electrode by sputtering. The morphology of the sputtered contacts was studied by scanning electron microscopy. The effect of postdeposition annealing on the recessed electrodes in silicon trenches was studied. The annealing process was carried out at 300°C for 10 min. The optoelectronic characteristics of MSM ultraviolet (UV) photodetectors with such trench electrodes in silicon substrates were studied in the dark and under UV illumination, comparing photodetectors based on annealed versus as-deposited samples. The electrical characteristics of photodetectors fabricated on annealed substrates revealed enhanced sensitivity to ultraviolet radiation. It was shown that annealing silver electrodes in silicon trenches can improve photodetector quality.