Advances in selective wet oxidation of AlGaAs alloys |
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Authors: | Choquette KD Geib KM Ashby CIH Twesten RD Blum O Hou HQ Follstaedt DM Hammons BE Mathes D Hull R |
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Affiliation: | Center for Compound Semicond. Sci. & Technol., Sandia Nat. Labs., Albuquerque, NM; |
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Abstract: | We review the chemistry, microstructure, and processing of buried oxides converted from AlGaAs layers using wet oxidation. Hydrogen is shown to have a central role in the oxidation reaction as the oxidizing agent and to reduce the intermediate predict As2O3 to As. The stable oxide is amorphous (AlxGa1-x) 2O3 which has no defects along the oxide/semiconductor interfaces but can exhibit strain at the oxide terminus due to volume shrinkage. The influence of gas flow, gas composition, temperature, Al-content, and layer thickness on the oxidation rate are characterized to establish a reproducible process. Linear oxidation rates with Arrhenius activation energies which strongly depend upon AlAs mole fraction are found. The latter produces strong oxidation selectivity between AlGaAs layers with slightly differing Al-content. Oxidation selectivity to thickness is also shown for layer thickness <60 nm. Differences between the properties of buried oxides converted from AlGaAs and AlAs layers and the impact on selectively oxidized vertical cavity laser lifetime are reported |
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