Structural Evolution During Formation and Filling of Self-patterned Nanoholes on GaAs (100) Surfaces

Nanohole formation on an AlAs/GaAs superlattice gives insight to both the "drilling" effect of Ga droplets on AlAs as compared to GaAs and the hole-filling process. The shape and depth of the nanoholes formed on GaAs (100) substrates has been studied by the cross-section transmission electron microscopy. The Ga droplets "drill" through the AlAs layer at a much slower rate than through GaAs due to differences in activation energy. Refill of the nanohole results in elongated GaAs mounds along the [01-1] direction. As a result of capillarity-induced diffusion, GaAs favors growth inside the nanoholes, which provides the possibility to fabricate GaAs and AlAs nanostructures.