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 $250nm$ thickness with selectively ion-implantation doped regions were released from a germanium-on-insulator substrate and integrated with a $175-μm$-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 $10μm$ exhibit an external quantum efficiency that varies from 5% at $411nm$ to 42% at $633nm$ under $−1V$ 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.