Refractive index and hygroscopic stability of AlxGa1−xAs native oxides

Abstract

We present prism coupling measurements on AIXGal.XAs native oxides showing the dependent~~c E!vE'D refractive index on composition (0.3 SXS0.97), oxidation temperature (400q<500), and carrier g purity. Index values range from n=l .490 (x=O.9, 400 "C) to 1.707 (x=O.3, 500 "C). The oxides are *)Electronicmail: dhall(j?nd.edu Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under Contract DE-AC04-04AL85000.

GaAs/AlOx Nonlinear Waveguides for Infrared Tunable Generation

“…Optical properties of AlOx have been characterized with discrepancies in the published results. AlOx transparency region has been unambiguously demonstrated to extend from deep UV (about 240 nm) up to 10 m, Hall et al, 1999) excepted an O-H absorption peak that we identified at 3 m (Ravaro et al, 2008). However several different values of the AlOx refractive index have been reported.…”

“…In the NIR these are included between 1.55 and 1.64, with a claimed dependence on the original Al composition. (Knopp et al, 1998;Hall et al, 1999;Durand et al, 2003) This is a major issue for the design of birefringent GaAs/AlOx nonlinear waveguides, as uncertainty on these properties affects the phase-matching wavelength of such devices. Selective oxidation of GaAs/AlAs waveguides is carried out in a quartz tube oven where samples are heated at 420-430°C while the atmosphere is saturated in water vapor by a 2 l/min flux of wet N 2 .…”

Reduction of etched AlGaAs sidewall roughness by oxygen-enhanced wet thermal oxidation

“…16 In general, conventional wet oxides of low Al-content AlGaAs are of inferior quality to those grown via O 2 -enhanced wet oxidation, as indicated by greater dissolution in the stain etch seen in Fig. 1͑a͒, much lower refractive index ͑1.45-1.5 vs 1.65-1.7͒, 15,17 and poorer adhesion. 16 While the images in Fig.…”

Low-loss nonselectively oxidized AlxGa1−xAs heterostructure waveguides

“…In particular, the presence of dilute O 2 during wet oxidation significantly increases the refractive index of Al 0.3 Ga 0.7 As from n ϳ 1.48 ͑no O 2 added͒ to n ϳ 1.68 ͑4000-7000 ppm O 2 ͒. 5,13 After cap layer removal, both the Al 0.3 Ga 0.7 As and Al 0.85 Ga 0.15 As layers are fully oxidized from the surface, resulting in an oxide single heterostructure planar waveguide. Details of the nonselective O 2 -enhanced wet oxidation process used in this work can be found in Ref.…”

“…5,6 Figure 1 shows a transverse electric ͑TE͒ prism coupling mode profile measured at 633 nm for the 1 m guiding layer structure after oxidizing for 88 min at 450°C with the addition of 7000 ppm O 2 ͑relative to the N 2 carrier gas͒. The waveguide structure schematic inset in Fig.…”