Electrochemical pore formation mechanism in III-V crystals - (Part I)

The anodic behavior of III-V crystals in electrolyte solutions was experimentally studied. The dependences of the pore-formation threshold voltage on the semiconductor composition and doping level, electrolyte solution composition and concentration, as well as the crystallographic orientation of the anodized surface, were obtained. Chemical and phase compositions of pore-formation reaction products in various semiconductor-electrolyte systems were studied. The structure of porous layers formed in GaAs, InP, and GaP crystals in aqueous and nonaqueous solutions was studied. The conditions for anisotropic propagation of pores in these crystals in the < 111 > V and < 111 > III directions were determined. The results obtained show that there is a fundamental difference of the chemical mechanisms of pore-formation reactions from mechanisms of anodic etching of III-V compounds.