Gallium arsenide antireflection layer via direct wet thermal oxidation

Broad bandwidth, low-reflectance, low-cost antireflection (AR) layers on GaAs are demonstrated using a quarter-wave optical thickness dielectric grown by directly oxidising the GaAs through a carefully-balanced oxygen-enhanced wet thermal process at 420°C. For centre design wavelengths between 550 and 800 nm, the native oxide AR layers have a simulated and measured reflectance minima as low as 1.0%, with reflectance <;10% over bandwidths as large as 342 nm. The experimental reflectance spectra agree well with the modelling based on the complex optical constants obtained by variable angle spectroscopic ellipsometry, and are consistent with the low GaAs native oxide surface roughness (<;0.3 nm) and interface roughness (<;2.3 nm) measured by atomic force microscopy.