Properties of atomic-layer-deposited ultra-thin AlN films on GaAs surfaces

Highlights: • Passivation of GaAs by plasma-enhanced atomic layer deposited AlN was investigated. • Photoreflectance results showed an effective ex situ passivation. • Photoluminescence confirmed the passivation effect. • Atomic force microscopy verified the substantially unaltered surface morphology. - Abstract: Properties and passivation effect of ultra-thin AlN films fabricated on InGaAs/GaAs near-surface quantum wells by plasma-enhanced atomic layer deposition are investigated. The role of the coating on the surface is studied by examining the electric field build-up by photoreflectance. Photoluminescence confirms the passivation effect with ultra-thin layers and the reduced electric fields with thicker AlN layers. Atomic force microscopy shows that an ultra-thin AlN layer does not substantially alter the surface morphology