Lateral wet oxidation of AlAs layer in GaAs/AlAs heterostructures grown byMBE on GaAs (n 1 1)A substrates

Lateral sidewall oxidation of AlAs layers grown on GaAs (1 0 0) and (n 1 1) A-oriented substrates (n = 1, 2, 3, or 4) within a heterostructure was stud ied. The oxidation rate for each type of substrate was measured between 390 degrees C and 450 degrees C. The oxidation data concerning the time depend ence of the oxidation rate was very well fitted by a theoretical formula ba sed on a Si oxidation model. The time dependence of oxidation rate followed a linear law for the initial process and successively a parabolic law. The oxidation rate is highly anisotropic which is related to the symmetry of t he crystal structure. An oxidation model was proposed from the results of a nisotropic activation energy of oxidation. AlxOy/GaAs DBRs (distributed Bragg reflectors) were fabricated and their re flection characteristics were measured. Tt is shown that the center wavelen gth of DBRs can be adjusted during the oxidation process. (C) 1999 Elsevier Science B.V. All rights reserved.