Microstructure of AlGaAs-oxide heterolayers formed by wet oxidation

Abstract

We have carried out a transmission electron microscopy based study of AlGaAs–Al(oxide) heterolayers created by lateral sidewall wet oxidation and identify the oxide phase formed as a consequence of the oxidation of AlAs to be γ-Al2O3, with the cubic Fd 3m structure. The oxide-semiconductor interface is weak and porous, possibly due to the high stress loads developed during oxidation, and we propose that the fast oxidation rates are a consequence of reactants transported to the oxidation front along the porous interface.

Growth of AlN and GaN Bulk Crystals from the Vapor Phase

“…The inlet of the tube was placed 3 mm above the BN susceptor, as shown in Figure 1. A differential pumping system was employed between the reactor and the mass spectrometer to maintain the working pressure in the spectrometer chamber below lxlO" 6 Torr. Before each measurement, conditions were allowed to stabilize for 20-30 minutes after any experimental variable was changed.…”

“…Munir et al [3] observed the formation of liquid Ga droplets at the ratio of -0.01 and no Ga droplets'at -0.033. Averyanova et al [8] calculated the critical ratio to be 3xl0" 6 to 3xl0" 5 in the temperature range 890°C-1080°C. The disagreement between the theory and experiment can be due to the uncertainty in evaluation of the sample area in the evaporation experiment.…”

“…It should be mentioned that the RHEED pattern indicates faceting of the surface when a large amount of material has been evaporated (several thousand angstroms). This could be partly due to an enhanced evaporation rate near defects or/and grain boundaries [6]. Ambacher et al [7] measured the flux of N 2 and the activation energy of 3.93 eV for GaN decomposition in vacuum by a quadrupole mass spectrometer (QMS).…”

Influence of Low Temperature-Grown GaAs on Lateral Thermal Oxidation of Al0.98Ga0.02As

“…The high quality of the oxide is attributed to the formation of stable AlO(OH) and Al 2 O 3 compounds [1]. However some problems related to the excess As created during the process, and weakness of the oxide interfaces, due to structural changes in the Al x Ga 1-x As layers, remain unsolved [2,3].…”

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

“…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. 2 Indeed, from the direct measurements performed on transmission electron micrographs of such samples, 2,13 a thickness contraction of 10%-20% is deduced.…”