Modeling the Lateral Wet Oxidation ofAlxGa1−xAsinto Arbitrary Mesa Geometries

Abstract

We report experimental and theoretical results on the lateral wet oxidation of bidimensional thin aluminum-rich layers into AlOx. We introduce a reaction-diffusion model of oxidation front propagation that includes effects of anisotropies and compare it to experimental results. This model can be used with any starting geometry, possibly nonconvex, and is deduced from the chemical reactions of wet oxidation of Al x Ga 1−x As -based layers. Numerical simulations performed with simple and complex geometries are in excellent agreement with the experimental observations. Our method is general and can apply to other oxides. It opens the way to the fine control of wet-oxidation fronts and to the formation of AlOx layers with a desired geometry that has numerous practical and relevant applications for, e.g., waveguiding or carrier confinement in photonics.

Selective wet oxidation of AlAsSb alloys on GaAs

“…As illustrated in Fig. 2 and already reported for instance in 17,47 , the aperture shape deforms throughout the oxidation duration. For circular etched mesas, the oxidation is observed to occur at rate very close to the fast-axis (along the (100) direction) value (see Fig.…”

“…The above-mentioned anisotropy can originate from a crystallographic dependence of the reactions 15,23 , from an anisotropic diffusion of the reactants or of the by-products through the formed oxide, or from an uneven distribution of the oxide-induced strain field 26 . In this particular study, except for the AlAs0.866Sb0.134 layer and as already observed for AlGaAs-layers on (001)-oriented substrates, the lateral oxidation of an AlAsSb layer from a circular (or a square) mesa leads to an oxide aperture whose shape can be described as a linear combination of a circle and a square 17,46,47 . The square fraction, s, (ranging from 1 for a square aperture to 0 for a circular aperture) can then be used as a quantifying parameter of the degree of oxidation anisotropy 23,46 .…”