InGaP Nano-pattern Structure Realized by Thermally Dewetted Au Nanoparticles and Anisotropic Dry Etching

Abstract

Background:: Optical reflection loss can be reduced more than 30% when multilayers ARC are deposited on the optoelectronic devices surface. Besides that, sub-wavelength structures, which have a period sufficiently smaller than the wavelength of light, have been introduced as an antireflection layer to offer a new possibility to suppress the Fresnel reflection. Normally, e-bean and nano-imprint lithography techniques are used to create nano-scale etch mask patterns. Metallic nanoparticles, which can be formed by a thermal dewetting process of metal thin film without any nanolithography techniques, can be utilized as an etch mask for the nano structure fabrications. The nano-patterned structures were fabricated on a silicon nitride passivation layer of a GaInP/GaAs/Ge triple-junction solar cell and showed an enhancement of its performance due to improved optical transmission and current matching. Objective:: Investigate the influences of InGaP nano-pattern structures on the optical characteristics and applied for compound solar cells. Method:: In this report, disordered InGaP nano-pattern structures were formed by thermally dewetted Au nanoparticles and anisotropic dry etching processes. The effects of the InGaP nano-patterned structure on the optical reflection characteristics were investigated. Results:: The result indicated that the InGaP nano-patterned structure can reduce the optical reflection in a wide range of wavelengths and, thus, can work as an antireflection layer. The InGaP nanostructure can improve up to 14.8% in the short circuit current density compared to that of the planar cell. Conclusion:: The InGaP nano structures have been successfully fabricated by thermal dewetted Au nanoparticles and anisotropic dry etching methods. The fabricated Au nanoparticles pattern was found to be the best when annealing temperature is 400°C for 30 minutes with the 5nm thick of Au film. By controlling dry etching time, the height of InGaP nanostructures can be varied from 95 nm to 150 nm. With the increasing of the height, the optical reflectance can be down to 22%. The InGaP nanostructure with the height of 150 nm was also introduced to the window layer of a single junction GaAs soar cell. The result indicated that the InGaP nanostructure only affects on the short circuit current density.