AlxGa1-xAs native-oxide-based distributed Bragg reflectors for vertical cavity surface emitting lasers

The problems associated with constructing AlxGa1-xAs native-oxide-based distributed Bragg reflectors (DBRs) for vertical cavity surface emitting lasers are investigated. Reflection and stability measurements are performed on structures with central lambda/2 cavities (lambda similar to 980 nm) of GaAs surrounded by two periods of native-oxide- based DBRs on the top and 2.5 periods on the bottom. Prior to crystal oxidation (H2O vapor + N-2, 430 degrees C) a period of the DBRs consists of similar to lambda/4 optically thick layer of GaAs and a thicker (oxidation) layer of AlxGa1-xAs (x = 0.95, 0.96, 0.97, 0.98, 1.00) surrounded by thinner (similar to 100 Angstrom) buffer layers that are AlyGa1-yAs (y = 0, 0.25, 0.50, 0.65, 0.070, 0.75, 0.80, 0.85). The DBRs are formed after oxidation of the high Al composition AlxGa1-xAs layers, and to some extent the AlyGa1-yAs buffer layers, forming a similar to lambda/4 optically x y thick layer of the native oxide. For comparison, more complicated DBRs are created by oxidizing superlattice layers. It is found that the AlxGa1-xAs composition, x, of the oxidation layer, choice of oxidizing or nonoxidizing AlyGa1-yAs buffer layers (y), oxidation parameters, and post-processing y parameters determine the DBR quality and stability, as well as the possibility of reoxidation. (C) 1998 American Institute of Physics. [S0021-8979(98)06422-6].