Lateral Oxidation of AlAs for Circular and Inverted Mesa Saturable Bragg Reflectors

Abstract

A model of the thermal oxidation kinetics that is based on the continuity equation is adapted to the fabrication of circular saturable Bragg reflector (SBR) mesa structures, as well as inverted mesa array structures. A comparison between theoretical calculations and experimental measurements shows good agreement, making the model a useful tool for the controllability of the structure-dependent oxidation process. The model is applied to the wet oxidation of buried AlAs layers for the fabrication of ultra-broadband, high index contrast, III-V/Al x O y SBRs. The rate of oxidation is found to be dependent not only on the oxidation temperature, but also on oxidation time, mesa geometry, and AlAs layer thickness. The two distinct large-area SBR structures, the circular mesa and the inverted mesa, are fabricated.

Anisotropy in the wet thermal oxidation of AlGaAs: influence of process parameters

“…Based on the profile of echniques and his methodolog an accuracy li en estimated to udy, we spann ssure, and moi hole) to check onitoring syste s traced with a ple of these in s Figure 2 depicts the time dependence measured for the inward oxidation of a 70-nm-thick AlAs layer carried out up to the full oxide closure from a 60-µm-diameter circular mesa. As previously reported and described by several papers [16,17], the oxidation evolves linearly, but tends to slightly accelerate when the aperture is about to close up. This effect, which deteriorates the process reproducibility when small apertures are targeted, is typical for mesa geometries for which the oxidizing front surface decreases against process time and can be reproduced by modelling [16][17][18][19].…”

“…As previously reported and described by several papers [16,17], the oxidation evolves linearly, but tends to slightly accelerate when the aperture is about to close up. This effect, which deteriorates the process reproducibility when small apertures are targeted, is typical for mesa geometries for which the oxidizing front surface decreases against process time and can be reproduced by modelling [16][17][18][19]. This final stage acceleration varies with the process temperature and the oxidized layer thickness.…”

Modeling the Lateral Wet Oxidation ofAlxGa1−xAsinto Arbitrary Mesa Geometries

“…The problem of the dynamics of wet oxidation of Al-rich thin layers has been tackled in several works [12,22,23]. Most models assume either planar or circular oxidation 2331-7019/19/11(4)/044067 (8) 044067-1 © 2019 American Physical Society geometries disregarding any anisotropies.…”

Low-loss buried AlGaAs/AlOx waveguides using a quasi-planar process

“…Although unimportant for this application, the lateral oxide/semiconductor interfaces were rough as a result of the coarse hole distribution and short oxidation distance. Since then, the latter process has also been applied to create contiguous oxide regions with sparse surface disruption to make highlyreflective mirrors over large areas [9] [10] or to facilitate epitaxial regrowth [11]. Furthermore, the availability of a process able to create buried oxide structures whilst maintaining a quasi-planar surface is considered to be particularly attractive when making multi-plane photonic devices such as mode-converted laser diodes [5] or vertically-coupled resonators [12], especially when the device layout requires lithographically-defined patterns of high resolution.…”