Prevention of gallium arsenide photocorrosion by an epoxy adhesion layer

Abstract

Coating of gallium arsenide with an adhesion layer of commercial epoxy prevented its photocorrosion. A two-component room temperature curing adhesive paste (Araldite 2014) has been selected. When GaAs/Araldite was employed as an anode in a three-electrode photoelectrochemical cell the photogenerated current density decreased significantly due to epoxy coating. However, depositing of few monolayers of Pt on GaAs surface prior to epoxy adhesion increased the photogenerated current density about four times. Moreover, impregnation of the epoxy film with gold enhanced the photogenerated current density significantly. The room temperature electrical conductivity of the epoxy films increased from 10−8 to 10−4Ω−1cm−1 due to gold impregnation. Enhancement of the photocurrent due to gold impregnation is attributed due to better conduction of the photogenerated holes into the electrolyte, also due to activating the adsorption of electrolyte ions.Several parameters are studied with the objective of determining the stability of epoxy films: these are continuous current–voltage (I–E) scans, prolonged illumination, weight changes and surface topography by scanning electron microscopy. All investigations have proven that the epoxy film was quite stable under anodic potentials and illumination in aqueous solutions.