Abstract
The native oxides of AIAs and AlGaAs have been studied for their use in device fabrication and their role in device reliability. Although, high-Al-composition AlGaAs is attractive for use in compound semiconductor devices because of its low index of refraction and large electronic band gap relative to GaAs, it decomposes quickly into a porous native oxide when exposed in a room-temperature environment.1 For example, we have observed a 30-μm diameter AlAs/GaAsInGaAs etched pillar that has deteriorated a distance of ~3 μm from the perimeter during 11 months in a typical room environment. Such etched pillar structures will therefore suffer long term reliability problems if used for a VCSEL. We present a process that seals an exposed AlAs layer against further oxidative decomposition. The sealant is formed by a rapid thermal anneal (RTA) to a temperature of ~500–600°C in forming gas after brief exposure of the AlAs surface to the typical room enviornment. The surface barrier layer thus formed is thin and impermeable to diffusing oxygen species, even at elevated temperatures, and can be thermally cycled. An important feature of the surface layer is its ability to fully block, and therefore mask, a steam oxidation of AlAs.2
© 1996 Optical Society of America
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