Light Trapping in Conformal Graphene/Silicon Nanoholes for High-Performance Photodetectors

Hybrid graphene/silicon heterojunctions have been widely utilized in photodetectors because of their unique characteristics of high sensitivity, fast response, and CMOS compatibility. However, the photoresponse is restricted by the high reflectance of planar silicon (up to 50%). Herein, an improved graphene/Si detector with excellent light absorption performance is proposed and demonstrated by directly growing graphene on the surface of silicon nanoholes (SiNHs). It is shown that the combination of SiNHs with conformal graphene provides superior interfaces for efficient light trapping and transport of the photoexcited carriers. A high absorption of up to 90% was achieved, and the conformal graphene/SiNH-based photodetectors exhibited a higher photoresponsivity (2720 A/W) and faster response (∼6.2 μs), compared with the counterpart of the planar graphene/Si, for which the corresponding values are 850 A/W and 51.3 μs. These results showcase the vital role of the material morphology in optoelectronic conversion and pave the way to explore novel high-performance heterojunction photodetectors.