The lateral oxidation of buriedAlxGa1−xAslayers with high Al content(x=0.8–1)is investigated, using an oxidation process in a wetN2+H2Oambient at 370–450 °C. The oxidation is clearly selective and significantly affected by process temperature, material composition,AlxGa1−xAslayer thickness, and the geometry of the oxidized structures. An asymptotic oxide growth with constant activation energies for the reactive process and for the transport mechanism is observed. The experimental oxidation behavior coincides well with a model of self-blocking pores. ©1997 American Institute of Physics.