Effects of polyimide passivation on the photoluminescence of high-purity epitaxial GaAs

Abstract

Polyimide has been used as interlayer dielectric and passivation material. We studied the optical passivation property of polyimide by examining the spectral changes in the photoluminescence (PL) spectra of high-purity epitaxial GaAs coated with polyimide. Before full cure, the polyimide is nearly transparent to visible and near-infrared radiation. After full cure, the typical PL of GaAs was unobservable at liquid nitrogen or higher temperatures, but clear and distinct at liquid-helium temperature. The resolution of the GaAs exciton spectrum was improved in the coated sample. The polyimide-GaAs system also resulted in very weak luminescence extending over a wide spectral range from the red to near infrared.