Ge micro-crystals photedetectors with enhanced infrared responsivity

Ge-on-Si micro-crystals grown on Si patterned substrates can be used as absorbing elements for photodetection in the near-infrared. In such microstructures light confinement effects, due to crystal faceting and pattern periodicity, enhance light absorption as compared to conventional epitaxial layers. The challenge in realizing this type of devices is the formation of a top transparent contact suspended on the microcrystal array. Graphene can be used as a suspended contact that can adapt to the 3D-morphology of the microcrystals, ensuring the formation of an electrically continuous layer. The fabricated devices feature a responsivity exceeding that of planar devices with comparable thickness.