High-Photoresponse and Broad-Band Graphene/WS₂/Porous-Si Heterostructure Photodetectors

Formation of pores on Si wafer as an effective approach to enhance the light absorption of Si is attractive for graphene (GR)-based-heterojunction optoelectronic devices such as GR/porous Si (PSi) photodetectors (PDs), but the misalignment at the GR/PSi interface limits further enhancement of the PDs’ performance. Here, we first employ WS2 as an interfacial layer between GR and PSi to fabricate GR/WS2/PSi heterojunction PDs exhibiting a broad-band photoresponse in the visible range, originating from the enlarged band gap of PSi based on the quantum confinement effect. By the insertion of the WS2 interfacial layer, the PDs’ parameters including responsivity, detectivity, and external quantum efficiency are greatly improved under reverse bias due to the increased built-in field throughout the device, resulting in better separation of the photoinduced electron–hole pairs. In addition, the response time of the PDs shows a sharp decrease in the GR/WS2/PSi structure compared to the GR/WS2/Si counterpart (102/228 → 2.46/1.16 μs for the rise/fall times in the transient photocurrent curve). A 20% loss of the responsivity value is observed after the stability of the PDs is tested during 2000 h in air, resulting from the passivation of WS2 for the GR and PSi surfaces.