## 2 Materials and Methods  
The cross-shaped carbon-based structure is illustrated schematically in Figure 1a and was fabricated as follows: Firstly, the s-SWCNT dispersions was prepared using the method reported in Reference [5]. Raw arc-discharge SWCNTs were purchased from Carbon Solution Inc. (Riverside, CA, USA). Dispersants 9-(1-octylonyl)-9H-carbazole-2,7-diyl (PCz) (Aladdin Industrial Corporation, Shanghai, China) and SWCNT (2 mg) were mixed in toluene (6 mL). The solutions were ultrasonicated with a top-tip dispergator (Sonics VC500, Newtown, Connecticut, USA) for 30 min at an amplitude level of 30% and were then centrifuged at 20,000\(\times\)\(g\) for 1 h (Allegra X-22R centrifuge, Beckman China Inc., Shanghai, China) to remove the bundles and insoluble material. The supernatants were collected for characterization and fabrication of photoelectrical devices. A dip-coating method was used to fabricate the uniform s-SWCNT film on wafer-scale Si substrates with 285 nm thermal oxide. The N-doped Si substrates were purchased from Suzhou Crystal Silicon Electronic & Technology Co., Ltd. (Suzhou, China). The thickness of the SiO\({}_{2}\) layer was allowed to fluctuate within a certain range, which did not affect the deposition of SWCNT film and the function of gate oxide in electrical characterization. The wafer-scale was immersed in SiO\({}_{2}\)/Si substrates in obtained supernatants for 6 h to form uniform s-SWCNT film. The as-fabricated s-SWCNT film was annealed at 450 \({}^{\circ}\)C for 15 min, which was carried out in an argon gas environment.  
After the fabrication of s-SWCNT film on SiO\({}_{2}\)/Si substrates, a lithographic and oxygen plasma process was used to fabricate the s-SWCNT film pattern (Figure 1a). The corresponding real optical and SEM images of the microstructure for s-SWCNT film are shown in Figure 1a,b respectively. Next, the chemical vapor deposition (CVD)-grown graphene was transferred on top of the s-SWCNT film and a second photolithography and oxygen plasma etch was used to fabricate a graphene channel (Figure 1a). The corresponding Raman spectrum in G-band regions for as-used graphene is shown in Figure 1c, in which the intensity ratio of I\({}_{\text{2D}}\)/I\({}_{\text{6G}}\) > 2.5 indicates the high crystal quality of the as-used graphene [22; 23]. Finally, source-drain electrodes were deposited with Au metal contacts (100 nm) using a photolithography and electron beam evaporation process. The Cr was used to improve Au adhesion to the graphene and s-SWCNT surface. The back-gate electrode was deposited with In metal contacts (50 nm).  
The SEM images were taken on a Zeiss Sigma 500 field-emission SEM system (Zeiss-China, Shanghai, China) with the acceleration voltage of 3 KV. A Renishaw RM3000 Raman microscope (laser: 514 nm with a 2 \(\upmu\)m spot size) (Renishaw Inc., Gloucestershire, England, UK) was used to perform the Raman spectra measurement. The atomic force microscopy (AFM) (Dimension ICON, Bruker-China, Beijing, China) observations were performed in the tapping mode. For photoresponse characterization, the continuous scanning wavelength photocurrent testing platform was constructed. The light source was a high-power supercontinuum source (SC-Pro) purchased from YSL Co., Ltd. (Wuhan, China) and a monochromator was used for automatic wavelength changing (YSL Co., Ltd. Wuhan, China) The electrical measurements were carried out in a cryogenic vacuum experiment system and the data were collected by a set of circuit systems consisting of the DC power (Yokogawa 7651, Tokyo, Japan), amperemeters (Keithely 2000, Tektronix-China Inc., Shanghai, China), preamplifiers (Exclusive C7a, Pioneer Inc., Tokyo, Japan), oscilloscopes (TDs5054B, Tektronix-China Inc., Shanghai, China), and Lock in amplifiers (SRS 830, SRS Inc., Sunnyvale, CA, USA).