The crystallographic anisotropy of the lateral selective thermal oxidation of AlGaAs alloys is experimentally studied. The anisotropic behavior of this oxidation process, used primarily for building a lateral confinement in vertical surface emitting lasers (VCSEL), is quantified by varying different process parameters and the geometrical shapes of laterally oxidized mesa structures. This experimental study aims to have a better control of the oxide aperture shape used in oxide-confined photonics devices.
In this letter, we report the first experimental demonstration of microdisk resonators that are vertically coupled to their buried access waveguides on III-V semiconductor epitaxial structures using an original fabrication process. The here-proposed and validated three-dimensional integration scheme exploits selective lateral thermal oxidation of aluminiumrich AlGaAs layers. Compared with the previously reported processing techniques, this new scheme is simpler as it does not require any planarization or substrate transfer steps. As a proofof-principle demonstration of this approach, 250-µm diameter microdisk devices exhibiting quality factor reaching ∼8500 have been successfully fabricated.
In this paper, an iterative method to model the anisotropic lateral oxidation of circular structures is proposed and validated by confrontation to experimental data. The described model enables the efficient calculation of the temporal bi-dimensional evolution of the oxidation front shape, starting from a circular mesa, and progressing inward as a result of an anisotropic process combining an isotropic diffusion with an anisotropic reaction. The result of the developed model shows that the oxide aperture smoothly deforms from a circle to become more diamond-like, mimicking the experimental situation encountered when fabricating Vertical-Cavity Surface-Emitting Lasers (VCSELs) on (100) wafers or, more generally, when oxidizing circular mesas of aluminum-containing III-V semiconductor on similarly oriented substrates.
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