Electrochemical Deposition of Iridium onto Gallium Arsenide from a Sulfamate Electrolyte Based on Hexachloroiridic(IV) Acid

Abstract

The nature of cathodic polarization in an iridium-plating electrolyte based on a sulfamate solution of H₂[IrCl₆] was studied. Spectroscopic analysis shows that the iridium electrolyte contains binuclear oxygen-bridged Ir(III, IV) sulfamate complexes. The microstructure and distribution profiles of the iridium deposit in contacts of different diameters were studied. The structure of the iridium deposit is highly dispersed. The nonuniformity of the iridium deposit profile over the contact area and the dependence of the deposit thickness on the contact diameter can be reduced by varying the hydrodynamic conditions of the metal electroplating (stirring of the electrolyte with a magnetic stirrer or ultrasound) and by using electrochemical polarization. The Ir–GaAs contacts with the Schottky barrier are characterized by high quality of electrophysical parameters and good reproducibility of the volt–ampere characteristics. A decrease in the thickness of the iridium deposit and of the n-GaAs epitaxial layer leads to an increase in the barrier height of the rectifying Ir–GaAs contacts.