Nonselective wet oxidation of AlGaAs heterostructure waveguides through controlled addition of oxygen

We present data showing that the addition of trace amounts of O-2 (< 1% relative to N-2) to N-2+H2O process gas during the wet thermal oxidation of AlxGa1-xAs enhances the oxidation rates of lower Al content (x <= 0.8) alloys (a tenfold increase for x = 0.3), while decreasing the oxidation rate selectivity R(x = 0.8)/R(x = 0.3) by a factor of seven. An increase in the refractive index from 1.49 to 1.68, and a fourfold decrease in surface roughness, indicates the formation of a denser, higher quality oxide for x = 0.3 AlGaAs. Oxides are characterized by prism coupling, atomic force microscopy, and scanning electron microscopy. Thermochemical calculations show a probable mechanism in the enhancement of the dry oxidation reactions of AlGaAs for low levels of O-2, while there is still an adequate quantity of H-2 produced to reduce As oxides in the wet oxidation process. An AlGaAs quantum well heterostructure p-n laser diode crystal is nonselectively oxidized to create a deep oxide, high-index contrast waveguide with potential applications in semiconductor photonic integrated circuits that require small bend radius, high isolation, low crosstalk optical waveguides.