Self-powered photodetector based on GaAs/single-walled carbon nanotube/graphene dual vdW heterojunction and surface passivation research

The GaAs surface is known to exhibit a high density of dangling bonds and surface states, which cause severe surface recombination and increase dark current. Passivation using (NH4)2S or NH4OH can form S-based or N-based passivation layers on the GaAs surface, effectively eliminating dangling bonds and decreasing the surface state density. Here, we demonstrate a GaAs/semiconducting single-walled carbon nanotube (SWCNT)/graphene dual van der Waals heterojunction photodetector by combining passivated GaAs with SWCNT networks and graphene. NH4OH and (NH4)2S were, respectively, used for the surface passivation of GaAs to evaluate the performance differences of the photodetectors. When irradiated with a 405 nm wavelength laser at a power density of 30 mW cm−2, the photodetector passivated with (NH4)2S exhibited a maximum short-circuit current density (Jsc) of 1.4 mA cm−2 and a specific detectivity (D*) of 2.3 × 1010 Jones, showing a significant improvement compared to the device passivated with NH4OH.