Convex nanoscale shells improve performance of photodetectors

According to KAUST, optical-cavity designs have sought efficiencies of light either by trapping the electromagnetic wave, or confining light to the active region of the device to increase absorption. Most use micrometre-or nanometre-scale spheres in which the light propagates around in circles on the inside of the surface, a phenomenon called whispering gallery mode.

Former KAUST scientist Der-Hsien Lien, a postdoctoral researcher at the University of California, Berkeley, and his colleagues from China, Australia and the US have shown that a more complex geometry comprising convex nanoscale shells improves the performance of photodetectors by increasing the speed at which they operate and enabling them to detect light from all directions. The work is described in Advanced Materials.

Surface effects play an important role in the operation of some devices, said KAUST principal investigator, Jr-Hau He. Nanomaterials offer a way to improve performance because of their high surface-to-volume ratio. “However, although nanomaterials have greater sensitivity in light detection compared to the bulk, the light–matter interactions are weaker because they are thinner,” said He. “To improve this, we design structures for trapping light.”