Surface energy model for the thickness dependence of the lateral oxidation of AlAs

Abstract

The lateral oxidation rate of AlAs layers decreases dramatically for layers thinner than about 500 Å, because the activation energies for the rate constant of the reaction at the oxidation front increases by an amount inversely proportional to the layer thickness. We derive a model for the thickness dependence of the lateral oxidation rate of AlAs based on the surface energy of the curvature observed at the oxide tip. From the model, we show that the linear oxidation rate has an exp(−θ0/θ) dependence on the AlAs layer thickness θ, and we can predict the slowing of oxidation when the AlAs layer is cladded with AlGaAs barriers. Also, we estimate the surface energy of the AlAs/oxide interface to be 50 eV/nm2.

Antimony segregation in the oxidation of AlAsSb interlayers

“…The oxidation rate of AlAs shows a strong dependence on the layer thickness when hр500 Å, where the thinner structures oxidize more slowly. 9 Linear oxidation rates are observed in thicker films between 400 and 500°C, where the oxidation is reactant limited.…”

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“…Temperature homogeneity across the wafer during the formation of the apertures must be better than 7 0:5 1C. The gallium content in the layer to be oxidized and its thickness is also very crucial [3,4]. Finally, the carbon concentration also plays an important role for the homogeneity of the current confinement layer and needs to be controlled precisely.…”

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“…Temperature homogeneity across the wafer during the formation of the apertures must be better than ±0.5 • C. Ga content of the current blocking layer is much more crucial [5], but can be controlled epitaxially very well. Oxide layer thickness is chosen to be larger than 30 nm although contribution to optical confinement is rather strong, but oxidation rates are much more sensitive on thickness variations for thinner layers [6]. Finally carbon concentration plays an important role for the homogeneity of the current confinement layer and needs to be controlled precisely with variations of less than ±5% during the growth of the current confinement layer, too.…”