Below 1% Reflectance for Black GaAs Surface Prepared by Facile Two-Step Wet Chemical Treatment: Hydrogen Peroxide and Water

To increase performance of many photonic devices (e.g., solar cell, light emitting diode (LED), photodetector), it is essential to decrease light reflection at device interfaces. Sustainable and scalable methods have been intensively developed for manufacturing nanostructured antireflection coatings at device surfaces to reduce the reflection-induced losses in them. In this work, a novel wet chemical method is demonstrated to prepare black nanostructured GaAs surfaces in scalable manner. This facile method includes two steps: immersion of GaAs in hot H₂O₂ solution followed by immersion in hot H₂O both at around 80 °C. Microscopy, spectroscopy, and diffraction measurements reveal that the H₂O₂ immersion increases a surface porosity at GaAs while the hot-water treatment causes the formation of GaOOH nanocrystals. Reflectivity at the resulting black GaAs surface is decreased even below 1% in a broadband. Photoluminescence intensity measurements are used to study whether the presented top-to-down method increases harmful non-radiative recombination, as compared to the initial GaAs surface. Integration of the found black-GaAs method with device manufacturing is presented by means of planar metal–GaAs–metal photodetectors, of which external quantum efficiency increases due to the method.