Graphene transfer passivates GaAs

Abstract

Graphene–semiconductor junction interface states influence the carrier recombination processes in emerging optoelectronic devices. The large density of interface states in the graphene–GaAs junction is partly formed by oxidation in air of the GaAs surface. A graphene transfer presented herein reduces the arsenic species in the GaAs oxide and maintains the reduction over a span of at least one year. The photoluminescence and terahertz emission spectra show reduced surface trapping of photogenerated carriers in GaAs with graphene-capped oxide. These findings demonstrate a 2D material transfer that passivates a 3D semiconductor surface. A consequence of the passivation is observed by photoreflectance modulation spectroscopy of graphene covered semi-insulating GaAs. The built-in surface field is sufficiently screened by optically pumped carriers to reveal an enhanced excitonic absorption just below the GaAs bandgap. The absorption critical point anomalously red shifts by 4–6 meV from the bulk exciton characteristic energy, an effect we attribute to the exciton absorption occurring closer to the graphene–GaAs interface and influenced by the near-surface GaAs dielectric polarization.