AlAs oxidation process in GaAs/AlGaAs/AlAs heterostructures grown by molecular beam epitaxy on GaAs (n11)A substrates

The lateral oxidation of AlAs layers grown on GaAs (100), (110) and (n11)A- oriented substrates (n = 1, 2, 3, 4) was studied. The temperature dependenc e of the oxidation rate was measured between 390 degrees C and 450 degrees C. The oxidation rate is highly anisotropic and the anisotropy is related t o the symmetry of the crystal structure. The oxidation process has an activ ation energy that depends on substrate orientation. The oxidation front lin e becomes irregular for temperatures higher than 450 degrees C and the surf ace of the samples was degraded when the temperature exceeded 540 degrees C . The time dependence of the oxidation rate was found to be similar to the Si oxidation process. (C) 1999 Elsevier Science Ltd. All rights reserved.