Flexible photodetectors on plastic substrates by use of printing transferred single-crystal germanium membranes

This letter presents studies of multiwavelength flexible photodetectors on a plastic substrate by use of printing transferred single-crystal germanium (Ge) membranes. Ge membranes of 250 nm thickness with selectively ion-implantation doped regions were released from a germanium-on-insulator substrate and integrated with a 175-mu m-thick polyethylene terephthalate substrate via a dry printing technique. Photodiodes configured in lateral p-i-n configuration using the flexible Ge membranes with an intrinsic region width of 10 mu m exhibit an external quantum efficiency that varies from 5% at 411 nm to 42% at 633 nm under -1 V bias condition. These results demonstrate the potential of utilizing single-crystal Ge-membrane photodiodes for imaging applications and as solar cells on objects with arbitrary curvatures and shapes.