Effects of electrical contacts on the photoconductive gain of nanowire photodetectors

The mechanism of the photoconductive gains of nanowire (NW) photodetectors has not been clearly explained yet, although it is generally thought to be the result of a long excess carrier lifetime due to a large trap density. Here, we demonstrate that the photoconductive gain of a Bi₂S₃ NW photodetector can be contributed by optical modulation of the electrical injection through contacts. We propose a quantitative model to explain the results based on a model of metal-nanowire contacts. The study shows that optically generated excess carriers can modify the barrier structure at the metal-nanowire interface and thereby increase photoconductivity.