Selective oxidation of buried AlGaAs versus AlAs layers

Abstract

We report significant differences between the properties of buried oxides converted from AlGaAs and AlAs layers using selective wet oxidation. Layers of AlxGa1−xAs with x≥0.96 exhibit crystallographic dependent oxidation rates, while for layers with x≤0.92 the oxidation rate is isotropic. Mesas containing partially oxidized layers of AlAs are unstable to rapid thermal cycling and exhibit excessive strain at the oxide terminus, while mesas containing partially oxidized layers of AlGaAs are robust and lack evidence of strain. Finally, the oxidation of AlGaAs layers, rather than AlAs, is found to provide robust oxide apertures for reliable vertical-cavity surface emitting lasers.

Strain in wet thermally oxidized square and circular mesas

“…17,18 Although our data support a faster oxidation in the ͗010͘ directions than in the ͓011͔ direction, the results obtained in this study do not follow the more generalized prediction of slower oxidation in the ͗011͘ directions. However, Li et al predict a different oxidation pro- file along the ͓011͔ and ͓011͔ directions because of the excellent polarization selection and control observed in oxideconfined VCSELs.…”

Low effective surface recombination in In(Ga)As/GaAs quantum dot diodes

“…Selective oxidation of the AlGaAs cladding layers, which has been extensively used in optoelectronic device fabrication, [12][13][14][15][16][17][18] was investigated here as a means to reduce the influence of the surface by reducing carrier diffusion to the etched surfaces. Some of the samples were placed in an oxidation furnace after the etch step to selectively oxidize the Al 0.9 Ga 0.1 As layers.…”

Local stress measurements in laterally oxidized GaAs/AlxGa1−xAs heterostructures by micro-Raman spectroscopy

“…Comparing the Al atomic densities in AlAs and in the ␥-Al 2 O 3 phase which has been reported to result from oxidation, 11,12 an important thickness contraction of up to 20% is expected for the oxidized layers. 2 Indeed, from the direct measurements performed on transmission electron micrographs of such samples, 2,13 a thickness contraction of 10%-20% is deduced. Stress induced by the lateral oxidation manifests itself as a mechanical instability of the multilayers for oxidized thicknesses of more than 300 nm.…”

“…1 In particular, vertical-cavity surface emitting lasers have been realized with such buried oxide layers acting as current limiting as well as optical confinement regions. 2 These devices have shown an important reduction of the threshold current in parallel with enhancement of the conversion efficiency, associated with the incorporation of the buried oxide layers. [3][4][5] This approach has also been proposed for the fabrication of GaAs-based metal-oxide-semiconductor field effect transistors, 6 large bandwidth Bragg mirrors, 7 optical elements ͑e.g., micro-lenses 8 ͒, and optical waveguides.…”

“…[3][4][5] This approach has also been proposed for the fabrication of GaAs-based metal-oxide-semiconductor field effect transistors, 6 large bandwidth Bragg mirrors, 7 optical elements ͑e.g., micro-lenses 8 ͒, and optical waveguides. 9 Among the various issues which are still not resolved with respect to this technique, the question of the strain induced in the layers is important, as on one hand it may affect the performance of devices 2 or their lifetime and on the other hand it may play a role in the oxidation process itself ͑modi-fication of the oxidation rate 10 ͒. Comparing the Al atomic densities in AlAs and in the ␥-Al 2 O 3 phase which has been reported to result from oxidation, 11,12 an important thickness contraction of up to 20% is expected for the oxidized layers.…”