Bismuth ferrite (BiFeO₃) based metal-semiconductor-metal photodetectors realized by the design of experiments approach

In this study, three different shapes (traditional, spiral, and enclosed) of interdigitated electrodes are designed and implemented on BFO photodetectors (PD). The electrode material used is indium tin oxide or ITO. As the dielectric layer, BFO is sputtered onto the silicon substrate via a radio frequency magnetron sputtering machine and annealed with a furnace tube. Eight experiments are planned according to the procedures set forth by the binary design of experiments (DOE) to optimize the PD fabrication steps. The three process parameters contemplated are annealing gases (nitrogen or oxygen), annealing temperature (300 and 550ºC), and sputtering argon flow rate (5 and 10 sccm). It can be found that regardless of the shape of interdigitated electrodes used, the responsivity and detectivity obtained from Run 3 (annealing temperature of 300ºC, argon flow of 10 sccm, and nitrogen annealing gas) are relatively large. In contrast, the corresponding values are all comparatively small in Run 5 (annealing temperature of 300ºC, argon flow of 5 sccm, and oxygen annealing gas). Furthermore, the interaction between the annealing temperature and the different annealing gases, as well as the argon flow alone, have noticeable influences on the responsivity and detectivity of the BFO photodetectors with the traditional interdigitated and spiral interdigitated electrodes. As for the PDs with the enclosed electrodes, the interaction between the annealing temperature and the different annealing gases also undeniably impacts the resultant responsivity and detectivity.