Photoconductive properties of polycrystalline selenium based lateral MISIM photodetectors of high quantum efficiency using different dielectrics as the charge blocking layer

We studied the photoconductive performance of polycrystalline selenium (pc-Se) based photodetectors with a lateral metal–insulator-semiconductor-insulator–metal (MISIM) device structure. The insulator layer is a 10 nm-thick Ga₂O₃, HfO₂, or Al₂O₃ thin film, and used as a charge blocking layer (CBL) to suppress dark current injected from the Al electrodes. The dark current suppression primarily depends on the barrier height of the junctions between the CBLs and electrodes. The Ga₂O₃ CBL exhibits a poor dark current suppression compared to the HfO₂ and the Al₂O₃ CBLs because of a lower electron barrier at the cathode. The lateral pc-Se photodetectors exhibit a very high internal photocurrent gain due to Fowler–Nordheim tunneling at relatively low applied voltages. The better crystallinity of pc-Se grains formed on the Ga₂O₃ CBL leads to a higher photoconversion efficiency for the MISIM-Ga₂O₃ photodetector. Compared with amorphous Se based lateral MISIM photodetectors, the pc-Se photodetectors demonstrate a uniform and much better photoconductive performance over the visible spectrum.