Abstract
Semiconductor nanowaveguides are the key structure for light-guiding nanophotonicsapplications. Efficient guiding and confinement of single-mode light in these waveguidesrequire high aspect ratio geometries. In these conditions, sidewall verticality becomescrucial. We fabricated such structures using a top-down process combining electronbeam lithography and inductively coupled plasma (ICP) etching of hard masksand GaAs/AlGaAs semiconductors with Al concentrations varying from 0 to100%. The GaAs/AlGaAs plasma etching was a single-step process using aCl2/BCl3/Ar gas mixture withvarious fractions of N2. Scanning electron microscope (SEM) observations showed that the presence of nitrogengenerated the deposition of a passivation layer, which had a significant effect on sidewallslope. Near-ideal vertical sidewalls were obtained over a very narrow range ofN2, allowing the production of extremely high aspect ratios (>32) for 80 nm wide nanowaveguides.
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