ADVANCES IN SELECTIVE WET OXIDATION OF ALGAAS ALLOYS

We review the chemistry, microstructure, and processing of buried oxid es converted from AlGaAs layers using wet oxidation. Hydrogen is shown to have a central role in the oxidation reaction as the oxidizing age nt and to reduce the intermediate product As2O3 to As. The stable oxid e is amorphous (AlxGa1-x)(2)O-3 which has no defects along the oxide/s emiconductor interfaces but can exhibit strain at the oxide terminus d ue to volume shrinkage. The influence of gas flow, gas composition, te mperature, Al-content, and layer thickness on the oxidation rate are c haracterized to establish a reproducible process. Linear oxidation sat es with Arrhenius activation energies which strongly depend upon AlAs mole fraction are found. The latter produces strong oxidation selectiv ity between AlGaAs layers with slightly differing Al-content. Oxidatio n selectivity to thickness is also shown for layer thickness <60 nm, D ifferences between the properties of buried oxides converted from AlGa As and AlAs layers and the impact on selectively oxidized vertical cav ity laser lifetime are reported.