Elemental diffusion during the droplet epitaxy growth of In(Ga)As/GaAs(001) quantum dots by metal-organic chemical vapor deposition

Abstract

Droplet epitaxy is an important method to produce epitaxial semiconductor quantum dots (QDs). Droplet epitaxy of III-V QDs comprises group III elemental droplet deposition and the droplet crystallization through the introduction of group V elements. Here, we report that, in the droplet epitaxy of InAs/GaAs(001) QDs using metal-organic chemical vapor deposition, significant elemental diffusion from the substrate to In droplets occurs, resulting in the formation of In(Ga)As crystals, before As flux is provided. The supply of As flux suppresses the further elemental diffusion from the substrate and promotes surface migration, leading to large island formation with a low island density.

Nucleation of Ga droplets self-assembly on GaAs(111)A substrates

“…Such a phenomenon was attributed to the onset of the Ostwald ripening process (the growth of large clusters on the cost of smaller ones and hence a decrease of the total cluster density in a closed thermodynamic system 26 ) with increasing the deposition temperature. The change in the density of DE InAs QDs on GaAs(001) grown by metal-organic chemical vapor deposition was also associated with the Ostwald ripening during the nucleation of In droplets 27 . In the present work we did not observe such a change of the Arrhenius slope.…”

Droplet-induced dot, dot-in-hole, and hole structures in GaGe thin films grown by MOCVD on GaAs substrates

“…1,2 This method, being different from the conventional Stranski-Krastanov growth mechanism where a lattice mismatch between the growing materials and the template/substrate is generally required and the grown structures are basically limited to QDs, 3,4 provides additional freedom for fabricating quantum structures, e.g., quantum rings and concentric multiple quantum rings. [5][6][7][8][9][10] The metal droplets, when heated without the presence of group V reaction species, induce backward melting of the template, which, followed by thermal evaporation of the remaining metal atoms of the droplets, leads to the formation of holes in the template. This process, so-called droplet etching (DETC) or drilling, has emerged and has been extensively studied in the past ten years.…”

“…[17][18][19][20][21] A careful literature survey shows that although DEPI and DETC studies are dominated by molecular beam epitaxy (MBE), explorations of DEPI by using metalorganic chemical vapor deposition (MOCVD) have started soon after MBE; 22,23 nevertheless, these studies are generally limited to III-V materials. 2,[5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] In comparison, DEPI and DETC studies on hetero-substrates are much fewer in the literature although heterogeneous material integrations, 1,23 e.g., III-V-on-Si/Ge, are highly desired for electrical and optoelectronic applications such as bipolar transistors, 24 tandem solar cells, [25][26][27] broadband photodetectors, 28 etc. 23,[29][30][31][32] Recent developments in surface plasmonics and metamaterials have seen many new applications of combining metallic nanoparticles and semiconductors in various configurations to enhance light absorption and/or scattering.…”