Interface recombination at the selectively wet-oxidized AlAs-GaAs interface

Abstract

The threshold of vertical cavity lasers has recently been greatly reduced by replacing proton implantation with selective 'wet oxidation' of the AlAs layers in Bragg reflectors to provide lateral confinement of both the electrical current and the optical mode. This paper reports on the effects of the oxidation on the surface recombination of GaAs at the interface with the oxide. It is shown that the GaAs surface is pinned very much like a free surface of GaAs exposed to air. On the other hand, if the GaAs is isolated from the AlAs by a thin layer of Al0.35Ga0.65As, then the GaAs/Al0.35Ga0.65As interface preserves the low surface recombination velocity of such interfaces.