Highly Efficient Broadband Photodetectors Based on the Lithography-Free Au/Bi2O2Se/Au Heterostructures
As one of the bismuth based oxychalcogenides materials, Bi2O2Se ultrathin films have received intense research interests attributed to the high carrier mobility, narrow bandgap, ultrafast intrinsic photoreponse and long-term ambient stability, exhibiting great potentials in the electronics and optoelectronics applications. However, the device performances of the photodetectors based on the metal/Bi2O2Se/metal structures were degraded due to the undesirable defects or contaminants from the electrodes deposition or the sample transfer process. In this work, highly efficient photodetectors based on the Au/Bi2O2Se junctions were achieved with the Au electrodes transferred under the assistance of a probe tip to avoid any contaminants from the traditional lighography methods. Furthermore, to improve the charge transfer efficiency or specifically the intensity of the elelctrical fields at the Au/Bi2O2Se interfaces and along the Bi2O2Se channel, the device annealing temperature was optimized to narrow the van der Waals gap at the Au/Bi2O2Se interface and the device channel length was shortened to improve the overall device performances. With all the efforts, the maximum device photoresponsivity was 9.1 A/W, and the device response time could approach 36 μs, besides, the photodetectors were featured as broadband spectral response from 360nm to 1090nm.