Kinetically controlled dewetting of thin GaAs cap from an ErAs/GaAs nanoparticle composite layer

ErAs metal nanoparticles (NPs) embedded in GaAs have multiple applications in plasmonic, terahertz, and tunneling devices. Growing a high quality thin GaAs layer over the ErAs NP layer is vital to these applications. In this work, the authors study the surface stability of a thin GaAs cap (1–5 nm) annealed in a temperature range of 450–620 °C. The thin GaAs cap covered a single layer of ErAs NPs [0.5–1.33 monolayer (ML)] grown using molecular beam epitaxy on GaAs(001) substrates at 450–500 °C. For 1.33 ML ErAs coverage, although a 1 nm GaAs cap exhibited a root-mean-square surface roughness close to 0.3 nm, the authors expected that 1 nm GaAs was not thick enough to overgrow the NPs in a height of 3–4 nm; thus, a large number of pinholes should be left on the surface. By increasing the GaAs cap thickness to 3 nm, the authors were able to achieve atomically smooth surfaces with few remaining pinholes. At a lower coverage of ErAs, 0.5 ML, the authors were able to achieve atomically flat pinhole-free GaAs ca...