The low-frequency impedance of anodically dissolving semiconductor and metal electrodes: A common origin?

The electrical impedance of p-type GaAs and InP semiconductor electrodes was studied in the potential region of anodic dissolution. In addition to the capacitive impedance loop observed at higher frequencies, an additional, inductive impedance loop is observed at lower frequencies. The characteristic frequency of this loop is proportional to the current density over several orders of magnitude. The proportionality constant between the characteristic frequency and the current density is the same for GaAs and InP electrodes and is independent of the electrolyte composition. In the literature, a low-frequency impedance loop is reported for p-type Si and for several metal anodes; remarkably, the published results also show that the characteristic frequency is proportional to the current density due to anodic dissolution and that the proportionality constant is the same as that observed with p-type GaAs and InP. These general features suggest that the low-frequency impedance behavior of dissolving semiconductor and metal electrodes reflects a common phenomenon inherent to anodic dissolution. In the discussion, it is suggested that this phenomenon might be related to the transport of ions through the rigid double-layer structure.