Anodic Dissolution and Selective Etching of Gallium Phosphide

Current voltage curves and the effective dissolution valence have been determined for GaP electrodes in 3 N NaOH solution. At electrode potentials of a few volts the current density for p‐type ( N A ∼ 4 ( 10 ) 17 · cm − 3 ) is a factor of 10 4 greater than for n‐type ( N D ∼ 4 ( 10 ) 17 cm − 3 ) electrodes. This difference allows selective removal of p material from p‐n structures. Application of this selective etching to the fabrication of mesa structures for GaP light emitting diodes, and to junction delineation, is discussed. At large current densities, 6 charges are transferred per dissolved GaP molecule in distinction to the 3 transferred charges found previously in alkaline solution at low ( < 2 mA cm − 2 ) current densities.