Black GaAs: Gold-Assisted Chemical Etching for Light Trapping and Photon Recycling

Abstract

Thanks to its excellent semiconductor properties, like high charge carrier mobility and absorption coefficient in the near infrared spectral region, GaAs is the material of choice for thin film photovoltaic devices. Because of its high reflectivity, surface microstructuring is a viable approach to further enhance photon absorption of GaAs and improve photovoltaic performance. To this end, metal-assisted chemical etching represents a simple, low-cost, and easy to scale-up microstructuring method, particularly when compared to dry etching methods. In this work, we show that the etched GaAs (black GaAs) has exceptional light trapping properties inducing a 120 times lower surface reflectance than that of polished GaAs and that the structured surface favors photon recycling. As a proof of principle, we investigate photon reabsorption in hybrid GaAs:poly (3-hexylthiophene) heterointerfaces.

Fabrication and Characterization of Black GaAs Nanoarrays via ICP Etching

“…They also proposed a qualitative reaction mechanism for anisotropic etching of GaAs and showed that reflectance of the roughened surface of black GaAs reduces up to ~ 50 times compared to polished wafers. In 2020, Paola Lova et al [ 25 ] proved that the etched GaAs (black GaAs) presented satisfactory light-trapping properties and the etched sample attracted more photon recycling. The articles mentioned above all proved that GaAs nanometer array structure has excellent photoelectric properties.…”

Fabrication and Characterization of Black GaAs Nanoarrays via ICP Etching

“…In 2016, Yun won Song et. al [23] [25]proved that the etched GaAs(black GaAs)presented satisfactory light trapping properties and the etched sample attracts more photon recycling. The articles mentioned above all proved that GaAs nanometer array structure has excellent photoelectric properties.…”

Gallium-V antireflective nanostructures by metal-assisted chemical etching for photodetector application

“…Etchant in GaAs MacEtch also involves combination of oxidant and acid. H2O2 [52][53][54][55][56][57][58][59][60] and potassium permanganate (KMnO4) [61][62][63][64][65][66][67][68][69][70][71] are widely used as oxidant while HF [52-62, 65, 67-71] and sulfuric acid (H2SO4) [63][64][66][67] are commonly used as acid. Patterned Au thin film is normally used as catalyst to fabricate ordered GaAs nanostructures [53-55, 59, 61, 63-64] while Au nanoparticles are used to fabricated disordered GaAs nanostructures [52,[58][59] .…”

“…H2O2 [52][53][54][55][56][57][58][59][60] and potassium permanganate (KMnO4) [61][62][63][64][65][66][67][68][69][70][71] are widely used as oxidant while HF [52-62, 65, 67-71] and sulfuric acid (H2SO4) [63][64][66][67] are commonly used as acid. Patterned Au thin film is normally used as catalyst to fabricate ordered GaAs nanostructures [53-55, 59, 61, 63-64] while Au nanoparticles are used to fabricated disordered GaAs nanostructures [52,[58][59] . In terms of etching characteristic, similar as Si MacEtch, GaAs MacEtch generally exhibits forward etching behavior, which means GaAs species underneath noble metal is etched.…”

“…This method could realize low surface reflection of less than 5% in 200-900 nm range [71] . The other method to form Au nanoparticles is to immerse GaAs wafer in gold trichloride (AuCl3) solution by reduction of Au 3+ to Au [52,58] . Due to the high density of Au particles deposited by this method, highly rough GaAs surface can be made, and the reflection of GaAs can be as low as 1% in visible-NIR wavelength range, which is referred as 'black GaAs'.…”